Revert "rustc-cg-gcc: fix script, again"

This reverts commit ab3d9ba.

Author: dkm

rust-cg-gcc/build.sh

@@ -96,6 +96,9 @@ CONFIG=("--enable-checking=release"
 
 libgccjit_path=$(dirname $(readlink -f `find "$PREFIX" -name libgccjit.so`))
 
+## Checkout rustc_cg_gcc
+git clone --depth 1 "${CG_GCC_URL}" --branch "${CG_GCC_BRANCH}"
+
 ## Download rustup and install it in a local dir
 ## Installs :
 ## - minimal profile