diff --git a/tools/build_cros_gcc b/tools/build_cros_gcc
index c04634a81..03711ccd8 100755
--- a/tools/build_cros_gcc
+++ b/tools/build_cros_gcc
@@ -1,178 +1,204 @@
 #!/bin/bash
 
+ set -e
+
+ # '\033[1;31m' outputs red text. '\033[0m' reverts it to normal.
+ command -v crew &>/dev/null || { echo -e "\033[1;31mcrew command not found.\033[0m"; exit 1; }
+
  GLIBC=glibc-$(crew search glibc -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
- BINUTILS=binutils-2.31.1
- GCC=gcc-8.2.0
- MPFR=mpfr-4.0.1
- GMP=gmp-6.1.2
- MPC=mpc-1.1.0
- ISL=isl-0.20
- CLOOG=cloog-0.18.4
+ BINUTILS=binutils-$(crew search binutils -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
+ GCC=gcc-$(crew search gcc -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
+ MPFR=mpfr-$(crew search mpfr -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
+ GMP=gmp-$(crew search gmp -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
+ MPC=mpc-$(crew search mpc -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
+ ISL=isl-$(crew search isl -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
 
- KERNEL_VERSION=$(crew search linuxheaders -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1).1
+ KERNEL_VERSION=$(crew search linuxheaders -v | tail -1 | cut -d' ' -f2 | cut -d'-' -f1)
 
- MAJOR_VERSION="$(echo $KERNEL_VERSION | cut -c1)"
+ MAJOR_VERSION="$(echo ${KERNEL_VERSION} | cut -c1)"
 
- case $1 in
- -h|--help) echo USAGE:
- echo \ $0 target arch_type prefix
- echo \ \-h, --help: Display this help
- echo \ \-v, --version: Display version
- echo \ \-t, --const: Display constants
- echo \ \-c, --clean: Clean current directory
- echo \ Valid targets: 'aarch64-cros-linux-gnu', 'x86_64-cros-linux-gnu', 'i686-cros-linux-gnu', 'armv7l-cros-linux-gnueabihf'
- shift
- exit 0;;
- -v|--version) echo build_cros_gcc version 1.26
- shift
- exit 0;;
- -c|--clean) rm -rf build-binutils build-gcc build-glibc
- rm -rf \
- ./$GCC \
- ./$CLOOG \
- ./$GMP \
- ./$GLIBC \
- ./$BINUTILS \
- ./$MPFR \
- ./$MPC \
- ./linux-$KERNEL_VERSION \
- ./$ISL \
- ./$GLIBC.tar.xz \
- ./$GMP.tar.xz \
- ./$GCC.tar.xz \
- ./$BINUTILS.tar.xz \
- ./linux-$KERNEL_VERSION.tar.xz \
- ./$MPFR.tar.xz \
- ./$CLOOG.tar.gz \
- ./$ISL.tar.bz2 \
- ./$MPC.tar.gz || true
- shift
- exit 0;;
- -t|--const)
- echo KERNEL_VERSION=$KERNEL_VERSION
- echo MAJOR_VERSION=$MAJOR_VERSION
- echo CLOOG=$CLOOG
- echo ISL=$ISL
- echo MPC=$MPC
- echo GMP=$GMP
- echo MPFR=$MPFR
- echo GCC=$GCC
- echo BINUTILS=$BINUTILS
- echo GLIBC=$GLIBC
- shift
- exit 0;;
- armv7l-cros-linux-gnueabihf)
- true;;
- aarch64-cros-linux-gnu)
- true;;
- i686-cros-linux-gnu)
- true;;
- x86_64-cros-linux-gnu)
- true;;
- *)
- echo Invalid target or option \'$1\'
- $0 -h
- exit 1;;
+ case x${1}x in
+   x-hx|x--helpx) echo Usage:
+     echo \ $0 target [jobs] [prefix]
+     echo \ \-h, --help: Display this help
+     echo \ \-v, --version: Display version
+     echo \ \-t, --const: Display constants
+     echo \ \-c, --clean: Clean current directory
+     echo \ Valid targets: 'aarch64-cros-linux-gnu', 'x86_64-cros-linux-gnu', 'i686-cros-linux-gnu', 'armv7l-cros-linux-gnueabihf'
+     exit 0;;
+   x-vx|x--versionx) echo build_cros_gcc version 1.27.1
+     exit 0;;
+   x-cx|x--cleanx) rm -rf build-binutils build-gcc build-glibc
+     rm -rf \
+     ./${GCC} \
+     ./${GMP} \
+     ./${GLIBC} \
+     ./${BINUTILS} \
+     ./${MPFR} \
+     ./${MPC} \
+     ./linux-${KERNEL_VERSION} \
+     ./${ISL} \
+     ./${GLIBC}.tar.xz \
+     ./${GMP}.tar.xz \
+     ./${GCC}.tar.xz \
+     ./${BINUTILS}.tar.xz \
+     ./linux-${KERNEL_VERSION}.tar.xz \
+     ./${MPFR}.tar.xz \
+     ./${ISL}.tar.bz2 \
+     ./${MPC}.tar.gz \
+     ./sha256sum || true
+     exit 0;;
+   x-tx|x--constx)
+     echo KERNEL_VERSION=${KERNEL_VERSION}
+     echo MAJOR_VERSION=${MAJOR_VERSION}
+     echo ISL=${ISL}
+     echo MPC=${MPC}
+     echo GMP=${GMP}
+     echo MPFR=${MPFR}
+     echo GCC=${GCC}
+     echo BINUTILS=${BINUTILS}
+     echo GLIBC=${GLIBC}
+     exit 0;;
+   xarmv7l-cros-linux-gnueabihfx)
+     true;;
+   xaarch64-cros-linux-gnux)
+     true;;
+   xi686-cros-linux-gnux)
+     true;;
+   xx86_64-cros-linux-gnux)
+     true;;
+   xx)
+     $0 -h
+     exit 1;;
+   x*x)
+     echo -e "\033[1;31mInvalid target or option '$1'\033[0m"
+     $0 -h
+   exit 1;;
  esac
 
- # '\033[1;31' outputs red text. '\033[0m' reverts it to normal.
- command -v crew > /dev/null || { echo "\033[1;31mcrew command not found.\033[0m"; exit 1; }
+ TARGET="$1" && shift
 
- if test ! $2; then
-   echo "$1" | grep x86_64 1>/dev/null
-   if [ $? == 0 ]; then
-   $0 $1 x86 $3;
-   exit 0;
-   fi
-   echo "$1" | grep i686 1>/dev/null
-   if [ $? == 0 ]; then
-   $0 $1 x86 $3;
-   exit 0;
-   fi
-   echo "$1" | grep armv7l 1>/dev/null
-   if [ $? == 0 ]; then
-   $0 $1 arm $3;
-   exit 0;
-   fi
-   echo "$1" | grep aarch64 1>/dev/null
-   if [ $? == 0 ]; then
-   $0 $1 arm64 $3;
-   exit 0;
+ if ! [[ "$1" =~ "^[0-9]+$" ]] &>/dev/null; then
+   JOBS="$1"
+   shift
+ else
+   shift
+ fi
+ if [[ -d $1 ]] &>/dev/null; then
+   PREFIX="$1"
+   shift
+ else
+   if ! [[ "$1" =~ "^[0-9]+$" ]] &>/dev/null; then
+     JOBS="$1"
+     shift
+   else
+     PREFIX="$1"
+     shift
    fi
  fi
- if test ! $3; then
-   $0 $1 $2 $(crew const CREW_PREFIX | cut -d'=' -f2)
-   exit 0
+ if [[ -z "${ARCH}" ]]; then
+   if { echo "${TARGET}" | grep x86_64 1>/dev/null; }; then
+     ARCH="x86_64";
+   fi
+   if { echo "${TARGET}" | grep i686 1>/dev/null; }; then
+     ARCH="x86";
+   fi
+   if { echo "${TARGET}" | grep armv7l 1>/dev/null; }; then
+     ARCH="arm";
+   fi
+   if { echo "${TARGET}" | grep aarch64 1>/dev/null; }; then
+     ARCH="arm64";
+   fi
+ fi
+ if [[ -z "${PREFIX}" ]]; then
+   PREFIX="$(crew const CREW_PREFIX | cut -d'=' -f2)"
+ fi
+ if [[ -z "${JOBS}" ]]; then
+   JOBS="$(nproc --all)"
  fi
 
- $0 -c
+ rm -rf \
+ ./${GLIBC} \
+ ./${GMP} \
+ ./${GCC} \
+ ./${BINUTILS} \
+ ./linux-${KERNEL_VERSION} \
+ ./${MPFR} \
+ ./${ISL} \
+ ./${MPC} \
+ ./sha256sum
 
- echo $1 $2 $3
+ wget -c https://ftpmirror.gnu.org/gnu/binutils/${BINUTILS}.tar.xz
+ wget -c https://ftpmirror.gnu.org/gnu/gcc/${GCC}/${GCC}.tar.xz
+ wget -c https://www.kernel.org/pub/linux/kernel/v"${MAJOR_VERSION}".x/linux-${KERNEL_VERSION}.tar.xz
+ wget -c https://ftpmirror.gnu.org/gnu/libc/${GLIBC}.tar.xz
+ wget -c https://ftpmirror.gnu.org/gnu/mpfr/${MPFR}.tar.xz
+ wget -c https://ftpmirror.gnu.org/gnu/gmp/${GMP}.tar.xz
+ wget -c https://ftpmirror.gnu.org/gnu/mpc/${MPC}.tar.gz
+ wget -c http://isl.gforge.inria.fr/${ISL}.tar.bz2
 
- wget https://ftpmirror.gnu.org/gnu/binutils/$BINUTILS.tar.xz
- wget https://ftpmirror.gnu.org/gnu/gcc/$GCC/$GCC.tar.xz
- wget https://www.kernel.org/pub/linux/kernel/v"$MAJOR_VERSION".x/linux-$KERNEL_VERSION.tar.xz
- wget https://ftpmirror.gnu.org/gnu/libc/$GLIBC.tar.xz
- wget https://ftpmirror.gnu.org/gnu/mpfr/$MPFR.tar.xz
- wget https://ftpmirror.gnu.org/gnu/gmp/$GMP.tar.xz
- wget https://ftpmirror.gnu.org/gnu/mpc/$MPC.tar.gz
- wget http://isl.gforge.inria.fr/$ISL.tar.bz2
- wget https://www.bastoul.net/cloog/pages/download/$CLOOG.tar.gz
+ SUMS="5d20086ecf5752cc7d9134246e9588fa201740d540f7eb84d795b1f7a93bca86  $BINUTILS.tar.xz\n"
+ SUMS+="832ca6ae04636adbb430e865a1451adf6979ab44ca1c8374f61fba65645ce15c  $GCC.tar.xz\n"
+ SUMS+="94efeb00e4603c8546209cefb3e1a50a5315c86fa9b078b6fad758e187ce13e9  $GLIBC.tar.xz\n"
+ SUMS+="87b565e89a9a684fe4ebeeddb8399dce2599f9c9049854ca8c0dfbdea0e21912  $GMP.tar.xz\n"
+ SUMS+="b587e083eb65a8b394e833dea1744f21af3f0e413a448c17536b5549ae42a4c2  $ISL.tar.bz2\n"
+ SUMS+="becc413cc9e6d7f5cc52a3ce66d65c3725bc1d1cc1001f4ce6c32b69eb188cbd  linux-$KERNEL_VERSION.tar.xz\n"
+ SUMS+="6985c538143c1208dcb1ac42cedad6ff52e267b47e5f970183a3e75125b43c2e  $MPC.tar.gz\n"
+ SUMS+="67874a60826303ee2fb6affc6dc0ddd3e749e9bfcb4c8655e3953d0458a6e16e  $MPFR.tar.xz"
+ echo -e "${SUMS}" > sha256sum
 
- for tar in *.tar*; do tar xpf $tar; done
+ if ! { shasum -a 256 -c sha256sum; }; then
+   echo -e "\033[1;31mChecksum mismatch. Please try again. :/ \033[0m";
+   exit 1;
+ fi
 
- rm -f \
- ./$GLIBC.tar.xz \
- ./$GMP.tar.xz \
- ./$GCC.tar.xz \
- ./$BINUTILS.tar.xz \
- ./linux-$KERNEL_VERSION.tar.xz \
- ./$MPFR.tar.xz \
- ./$CLOOG.tar.gz \
- ./$ISL.tar.bz2 \
- ./$MPC.tar.gz 
+ for tar in *.tar.*; do echo "Extracting ${tar}..." && tar xpf ${tar}; done
 
- cd $GCC
- ln -s ../$CLOOG cloog
- ln -s ../$ISL isl
- ln -s ../$MPC mpc
- ln -s ../$GMP gmp
- ln -s ../$MPFR mpfr
+ cd ${GCC}
+ GCC_PATCHES="gcc-8.2.0-isl-0.20.patch"
+ for PATCH in ${GCC_PATCHES}; do
+   wget https://github.com/JL2210/patches/raw/master/${PATCH}
+   patch -Np1 -i ${PATCH}
+ done
+ ln -s ../${ISL} isl
+ ln -s ../${MPC} mpc
+ ln -s ../${GMP} gmp
+ ln -s ../${MPFR} mpfr
  cd ..
  mkdir build-binutils || true
  cd build-binutils
- ../$BINUTILS/configure --prefix=$3 --target=$1 --disable-multilib
- make -j$(nproc)
+ ../${BINUTILS}/configure --prefix=${PREFIX} --target=${TARGET} --disable-multilib
+ make -j${JOBS}
  make install
  cd ..
- cd linux-$KERNEL_VERSION
- make ARCH=$2 INSTALL_HDR_PATH=$3/$1 headers_install
+ cd linux-${KERNEL_VERSION}
+ make ARCH=${ARCH} INSTALL_HDR_PATH=${PREFIX}/${TARGET} headers_install
  cd ..
  mkdir build-gcc || true
  cd build-gcc
- ../$GCC/configure --disable-libmpx --prefix=$3 --target=$1 --enable-shared --enable-host-shared --enable-languages=c,c++,fortran,go --disable-multilib
- make -j$(nproc) all-gcc
+ ../${GCC}/configure --prefix=${PREFIX} --target=${TARGET} --enable-shared --enable-host-shared --enable-languages=c,c++,fortran,go --disable-multilib --disable-libmpx
+ make -j${JOBS} all-gcc
  make install-gcc
  cd ..
  mkdir build-glibc || true
  cd build-glibc
- ../$GLIBC/configure --disable-libmpx --prefix=$3/$1 --enable-shared --enable-host-shared --build=$MACHTYPE --host=$1 --target=$1 --with-headers=$3/$1/include --disable-multilib libc_cv_forced_unwind=yes
+ ../${GLIBC}/configure --prefix=${PREFIX}/${TARGET} --enable-shared --enable-host-shared --build=${MACHTYPE} --host=${TARGET} --target=${TARGET} --with-headers=${PREFIX}/${TARGET}/include --disable-multilib --disable-werror libc_cv_forced_unwind=yes
  make install-bootstrap-headers=yes install-headers
- make -j$(nproc) csu/subdir_lib
- install csu/crt1.o csu/crti.o csu/crtn.o $3/$1/lib
- $1-gcc -nostdlib -nostartfiles -shared -x c /dev/null -o $3/$1/lib/libc.so
- touch $3/$1/include/gnu/stubs.h
+ make -j${JOBS} csu/subdir_lib
+ install csu/crt1.o csu/crti.o csu/crtn.o ${PREFIX}/${TARGET}/lib/
+ ${TARGET}-gcc -nostdlib -nostartfiles -shared -x c /dev/null -o ${PREFIX}/${TARGET}/lib/libc.so
+ touch ${PREFIX}/${TARGET}/include/gnu/stubs.h
  cd ..
  cd build-gcc
- make -j$(nproc) all-target-libgcc
+ make -j${JOBS} all-target-libgcc
  make install-target-libgcc
  cd ..
  cd build-glibc
- make -j$(nproc)
+ make -j${JOBS}
  make install
  cd ..
  cd build-gcc
- make -j$(nproc)
+ make -j${JOBS}
  make install
  cd ..
- $1-gcc -v
+ ${TARGET}-gcc -v