Add sanitizer features to unix_cc_toolchain_config

[oliverlee]

There was some discussion here about adding asan, tsan, and ubsan features to the unix toolchains to match macos. bazel-contrib/toolchains_llvm#90 (comment)

I've taken my changes local to that project and copied it into Bazel as suggested by @fmeum. I've written some tests but I'm not sure where to place them or if it makes sense to depend on the error messages from asan/tsan/ubsan.

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[fmeum]

https://cs.opensource.google/bazel/bazel/+/3748bcc8bf0c45e34295583fafaf1f52449114b8:src/test/shell/bazel/cc_integration_test.sh;l=0 runs on Linux and macOS, I think that tests would fit in there.

[oliverlee]

Is there a suggestion for handling platforms without sanitizer libraries to link against?

https://storage.googleapis.com/bazel-untrusted-buildkite-artifacts/01855fff-0611-4e48-957c-fd2a745c57f7/src/test/shell/bazel/cc_integration_test/shard_3_of_5/test.log

ld.gold: error: cannot find -lasan"

[fmeum]

@oliverlee Looks like the failure is with gcc on an old centos, which would be rather difficult to match with Bazel platform constraints. Instead, since the feature is opt-in anyway, you could check for gcc and its version in the integration test and skip the test if it isn't supported.

The ASan test failure on macOS may be missing due to compiler optimizations as the example code doesn't really do anything. We have found these examples trigger ASan and UBSan relatively reliably across platforms.

[oliverlee]

@fmeum I've updated tests to check for lib*san on Linux since is seems that centos is using gcc 10.

It also looks like you're right about compiler optimizations so I've locally disabled optimizations with volatile in the asan example. Let me know if you would prefer the sample you provided.

[fmeum]

LGTM, but this needs a team member's approval. @oquenchil, would you be available to review this PR?

[oliverlee]

Thanks for reviewing and especially @fmeum for all your help.

[fmeum]

@bazel-io flag

[ShreeM01]

@bazel-io fork 6.1.0