[clang] [clang] Fix darwin-related tests' REQUIRES annotation (PR #130138)

[Steven Wu via cfe-commits]

cachemeifyoucan wrote:

Do you have a bot or build to point to for test failures?

There is no way to disable Darwin target from clang driver. I think the test might be related to the host platform is not Darwin so the driver didn't infer the target correctly without a default target triple?

I can see two fixes:
* Maybe pass a platform for the failing tests so there is no need for `system-darwin` or `target` for REQUIRES
* The bot should pass the correct host target triple otherwise the clang driver might just not function correctly when you cross-compile.

https://github.com/llvm/llvm-project/pull/130138