llvm: Install cross-compiler wrappers instead of GCC

Move clang wrappers installation to llvm package. This
avoids upreving GCC ebuilds for future clang only wrapper
changes.

BUG=b:186803617
TEST=CQ, SDK tryjobs

Change-Id: Ie81d6fa6be36a48019ccbd0ef8eed2a262261f7b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/3049972
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
8 files changed