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

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

The changes look correct to me, but I added Eli and Alexey for some other opinions to be sure.

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