compiler_wrapper: pass --prefix argument to clang

ToT clang needs --prefix is needed to find the correct tools.

BUG=chromium:1182224
TEST=Updated compiler wrapper in SimpleChrome, nacl builds.

Change-Id: I8073e1a5482a23f38bb1e0d88e2b31ee2d97fa6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2721199
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
32 files changed