wrapper: allow Android to specify their own llvm-flags

Given the discussion on
https://android-review.googlesource.com/c/platform/external/toolchain-utils/+/1330695,
it sounds like our Android friends want to be able to tweak llvm-next
flags without going through chromium-review + having to pull their
changes back into Android.

This CL allows them to make changes to their llvm-next flags entirely
locally, and isolates CrOS' llvm-next flags from Android's.

BUG=None
TEST=Built the wrapper for CrOS and Android.

Change-Id: If1bcfe762a4f368db9816557752651edc877f497
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2247003
Reviewed-by: Pirama Arumuga Nainar <pirama@google.com>
Reviewed-by: Tiancong Wang <tcwang@google.com>
Tested-by: George Burgess <gbiv@chromium.org>
3 files changed