env-setup.sh: Remove GNU tools in the Docker image before building

This will help ensure that the GNU tools aren't hard coded anywhere as
the goal of the LLVM tools is to be as compatible as possible.

Closes: ClangBuiltLinux#122
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

env-setup.sh

@@ -20,3 +20,17 @@ ccache --set-config=cache_dir=/travis/.ccache
 
 # Clear out the stats so we actually know the cache stats
 ccache -z
+
+# Ensure that GNU tools are not available when using LLVM tools
+function remove() {
+    type -a "${@}" | awk '{print $3}' | while IFS=$'\n' read -r line; do rm -vf "${line}"; done
+}
+case ${ARCH:=arm64} in
+    arm32*) CROSS_COMPILE=arm-linux-gnueabi- ;;
+    arm64) CROSS_COMPILE=aarch64-linux-gnu- ;;
+    ppc32) CROSS_COMPILE=powerpc-linux-gnu- ;;
+    ppc64le) CROSS_COMPILE=powerpc64le-linux-gnu- ;;
+esac
+remove "${CROSS_COMPILE:-}"ar
+remove "${CROSS_COMPILE:-}"gcc
+[[ ${LD} =~ ld.lld ]] && remove ${CROSS_COMPILE:-}{ld,ld.bfd,ld.gold}