Add supports_interface_shared_libraries to cc_shared_library

[keith]

This also backfills tests and fixes this in the default unix toolchain

[keith]

i could split the unix toolchain fix up but it was nice to verify with this new support

[keith]

this is still off by default and requires users pass --features=supports_interface_shared_libraries

[keith]

this working on macOS depends on #675

[keith]

cc @fmeum in case there was a reason not to do this originally

[fmeum]

I don't see why it shouldn't work.

[lilygorsheneva]

Getting a failure in tests that are still in main Bazel repo.
https://github.com/bazelbuild/bazel/blob/708b25f5716af27cce53c797d149a73bf2dbdf66/src/main/starlark/tests/builtins_bzl/cc/cc_shared_library/test/BUILD.builtin_test#L367

value of: collection
1 expected elements missing from values:
  0: -lprivate_lib_so

Investigating.

[lilygorsheneva]

Disabling interface_shared_objects in that test fixes it; that being said is the change in default behavior expected? Still waiting on additional testing to see if this breaks actual users.

[keith]

can you tell from the log if there's a nodeps version of that lib in there? i think disabling that feature is fine for the tests, i guess that test is using the default --dynamic_mode value so it really is changing what is linked

[lilygorsheneva]

A .../libprivate_lib_so.ifso appears in the list

[keith]

yea i think that behavior is an expected change here. but if that test also works on macOS we probably still need to disable this feature for it. i think we should just disable that feature since it's unrelated to simplify

[pzembrod]

Hi Keith, could you sync this PR to head again? It looks like I'll need to manually import it to double-check internal test failures, and the import fails with "Cannot find a merge reference for Pull Request 680. It might have a conflict with head."

[keith]

rebased and green! conflicts were just adding new features in the tests in 2 prs at once