compiler_wrapper: search compiler executable in $PATH

Search the compiler executable in the directories named by PATH
environment variable and add its parent directory as PYTHONPATH to
locate bisect_driver.py

BUG=chromium:1121018
TEST=verified locally

Change-Id: If1c397bedfc03b929d73ae490c1bb8f11b4edea5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2415130
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Jian Cai <jiancai@google.com>
1 file changed