[clang] [llvm] [ARM] Adding diagnostics for mcmodel=tiny when used in invalid targets (PR #125643)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay requested changes to this pull request.

We typically add such incompatibility check in clang/lib/Driver instead of clang/lib/Frontend.

(Apologies, I will have limited internet access between April 20th and May 4th, and my response time may be delayed.. Happy if a regular clang maintainer is happy.)


https://github.com/llvm/llvm-project/pull/125643