Avoid deduplicating linkopts of cc_shared_library dependencies.

[katzdm]

Linker inputs for dependencies of cc_shared_library are currently passing their linkopts as a depset, which leads to deduplication of the flags thereby passed. Consequently, a sequence of well-formed flags like -framework Security -framework IOKit gets collapsed to -framework Security IOKit; the linker then interprets IOKit as an object file that it's unable to locate, which yields a malformed link line.

Passing linkopts directly rather than wrapping it in depset appears to resolve the issue. I've added a test that replicates the original issue; since -framework isn't meaningful on all platforms, I've only enabled it for MacOS.

Note that the tests in this repository utilize the rules_cc repository rather than the built-in rules; therefore, I don't think the new test can be expected to pass until the change has been propagated there, and the controlling MODULE.bazel.lock entry has been updated. I've tested it locally by cating a local_path_override directive to the MODULE.bazel file that gets synthesized for these tests, in order to point the tests towards a local fork of rules_cc with this same change applied; under these conditions, the test passes.

Closes #27735.

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[fmeum]

@bazel-io fork 9.0.0

[bharadwaj08-one]

@katzdm Could you please take a look at the failing checks?

[katzdm]

@bharadwaj08-one Please see the explanation in the PR description:

Note that the tests in this repository utilize the rules_cc repository rather than the built-in rules; therefore, I don't think the new test can be expected to pass until the change has been propagated there, and the controlling MODULE.bazel.lock entry has been updated. I've tested it locally by cating a local_path_override directive to the MODULE.bazel file that gets synthesized for these tests, in order to point the tests towards a local fork of rules_cc with this same change applied; under these conditions, the test passes.

[katzdm]

@bharadwaj08-one friendly ping here, just checking that there's no work needed on my end.

[pzembrod]

Thanks for doing this. Not only does it fix an error (that I wasn't aware of), it also cleans up tech debt.

From https://bazel.build/rules/lib/toplevel/cc_common#create_linker_input:

user_link_flags None; or depset of strings; or sequence of strings; default is None User link flags passed as strings. Accepts either [String], [[String]] or depset(String). The latter is discouraged as it's only kept for compatibility purposes, the depset is flattened. If you want to propagate user_link_flags via unflattened depsets() wrap them in a LinkerInput so that they are not flattened till the end.

[iancha1992]

@katzdm @pzembrod Could you please take a look at the presubmit failure? Thanks!

[katzdm]

@iancha1992 Please see the explanation in the PR description:

Note that the tests in this repository utilize the rules_cc repository rather than the built-in rules; therefore, I don't think the new test can be expected to pass until the change has been propagated there, and the controlling MODULE.bazel.lock entry has been updated. I've tested it locally by cating a local_path_override directive to the MODULE.bazel file that gets synthesized for these tests, in order to point the tests towards a local fork of rules_cc with this same change applied; under these conditions, the test passes.