bazel --strip=never seems to not working with fastbuild

[Quyen Le]

I used bazel 4.0.0 to compile our project. We want to keep debug symbols in `fastbuild` config but no matter what we did, the debug symbols were always stripped.

bazel build //... --strip=never

For example with the above command, the final binary's debug symbols still got stripped.

Note we did use copts = [ "-g"] in several of our targets's BUILD files (we don't use --copts command line option because not all targets need debug symbols).