[clang] [llvm] [Clang][SME] Detect always_inline used with mismatched streaming attributes (PR #77936)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

clang has never emitted diagnostics for failure to inline an always_inline function.  But if gcc is doing it, maybe defaulting to an error isn't such a big deal.

Separately, it's probably worth ensuring that the LLVM inlining passes don't actually perform illegal inlining for functions marked always_inline; looking at the code, it looks like we might end up skipping the relevant checks.

https://github.com/llvm/llvm-project/pull/77936