add missing runtime deps to ALL core packages, add getrealdeps script (#7472)

* gcc: add missing zlibpkg dep

* add getrealdeps script

* add color

* suggested changes from @supechicken

* suggested changes

* fix verbiage

* add NOCOLORS option

* use read in lieu of head, and do not check nonexistent files

* Exit early if wrong package name is given.

* Add some quick exit code

* Allow for pkg.rb in getrealdeps and also add deps to all core packages

* fix lint error

* fix zlibpkg

* cleanup gcc deps

* move filecmd to be a ruby dependency

* fix llvm deps

* lint fix

* update more deps

* make sure package is installed before checking for deps

* add more deps

* change verbiage

* add more deps

* more dep updates

packages/diffutils.rb

@@ -22,6 +22,7 @@ class Diffutils < Package
      x86_64: 'edddafc3090b7b146594d3b3d80c3c4cb8730c662b68eaaf2d90b42824368eb3'
   })
 
+  depends_on 'glibc' # R
   depends_on 'libsigsegv'
 
   def self.build