Add clang to ere-base (#119)

Signed-off-by: Ignacio Hagopian <jsign.uy@gmail.com>

docker/base/Dockerfile.base

@@ -13,6 +13,7 @@ ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
     build-essential \
+    clang \
     cmake \
     pkg-config \
     curl \