Document how to build licenses_cpp #174942
Description
In one of my PRs, I got a license check failure: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8704706045168736321/+/u/test:_Run_license_cpp/stdout
The message at the end says:
The license check can be repeated locally with //engine/src/flutter/ci/licenses_cpp.sh
but when I tried that, it didn't work:
No host profile directory specified. Guessing based on architecture: arm64
ERROR: Executable not found at the expected path: /Users/mdebbar/github/flutter/engine/src/flutter/ci/../../out/host_profile_arm64/licenses_cpp
Please ensure the project has been built and this script is in the correct location.
At no point was I told how to build the licenses_cpp executable.
cc @gaaclarke