Disable -Werror on unused-command-line-argument

[DonggeLiu]

Some projects use -Werror to turn all warnings into errors.
This affects Centipede as we do not separate build and linking flags as it expects, which leads to unused-command-line-argument warnings.
This PR disables turning that specific warning into errors and keeps the rest the same.

[DonggeLiu]

@oliverchang: I reckon this solution is cleaner than what we discussed.

1. It does not need a wrapper cc.
2. It only ignores that specific kind of warnings/errors and keeps the rest the same.

Would you think this could be a good solution? Thanks!

[DonggeLiu]

/gcbrun trial_build.py all --sanitizer address --fuzzing-engine centipede

[oliverchang]

nice solution! is this heavily dependent on the order of flags though? i.e. is there a dependency on the -Werror coming before/after what we specify here?

[DonggeLiu]

nice solution! is this heavily dependent on the order of flags though? i.e. is there a dependency on the -Werror coming before/after what we specify here?

Nope, I tested it locally: it can come either before or after -Werror.

[oliverchang]

nice solution! is this heavily dependent on the order of flags though? i.e. is there a dependency on the -Werror coming before/after what we specify here?

Nope, I tested it locally: it can come either before or after -Werror.

This is great then :) Nice suggestion!

[DonggeLiu]

/gcbrun trial_build.py all --sanitizer none --fuzzing-engine centipede

[DonggeLiu]

/gcbrun trial_build.py all --sanitizer address --fuzzing-engine centipede

This failed only on project wuffs due to running out space:

OSError: [Errno 28] No space left on device

I tested Centipede on wuffs locally and it passed the build test.
The test creases an 8G build/, consisting of a 5.5G out/ and a 2.6G work/, we probably should consider limiting its size.
As a comparison, the build/ dir created by github-scarecrow was 7.7M.