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

[Fangrui Song via llvm-commits]

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@@ -391,6 +391,7 @@ Improvements to Clang's diagnostics
 
 
 - An error is now emitted when a ``musttail`` call is made to a function marked with the ``not_tail_called`` attribute. (#GH133509).
+- The ``-mcmodel=tiny`` option will now be diagnosed on all targets other than ARM or AArch64.
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MaskRay wrote:

The commit message/description and the note should be changed. Only X86 is affected. This change is pretty niche and does not deserve a release note.

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