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

[Lucas Duarte Prates via cfe-commits]

pratlucas wrote:

> Maybe pass a platform for the failing tests so there is no need for system-darwin or target for REQUIRES

Do you mean by adding a `--target` option to the tests? I think this would also be a valid solution, but I can't tell if this would go against the original intent of the tests. (i.e. were they designed to test these options combined with the default triple inference? Or the options alone?)

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