Disable -Werror on unused-command-line-argument (#9030)
Disable -Werror on unused-command-line-argument (#9030)

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.
google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz