[clang] [clang] Enhance handling of Apple-specific '-arch'/'-target' option values (PR #72821)

[James Y Knight via cfe-commits]

jyknight wrote:

I don't think this is a good idea.

Not only is that weird to magically switch to an apple build from a non-apple platform, this is also not even a particularly useful behavior for an Apple platform, where "darwin" is basically deprecated, and you're supposed to use a target of x86_64-apple-macos11 (or ios/watchos/etc).

https://github.com/llvm/llvm-project/pull/72821