Initial version of a go version of the compiler wrapper.

Still calls the old wrapper if one of the following flags is given:
- Xclang-path
- clang-syntax
- env WITH_TIDY
- env FORCE_DISABLE_WERROR
- env GETRUSAGE
- env BISECT_STAGE

BUG=chromium:773875
TEST=Unit tests that also verify the produced command against the
TEST=existing compiler wrapper.

Change-Id: I1e0a720ce9f485d8015deefb2682f2cb760d82e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1652057
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Tobias Bosch <tbosch@google.com>
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Tobias Bosch <tbosch@google.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
36 files changed