[clang] [Clang] fix crash in codegen caused by deferred asm diagnostics under -fopenmp (PR #147163)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

I think calling targetDiag() should stop codegen.  And if that works correctly, this patch is unnecessary.

https://github.com/llvm/llvm-project/pull/147163