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

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> My understanding is that "recoverable" in this context means we can actually generate sensible IR for the construct. So no errors, except for warnings promoted to errors (or certain errors which don't impact IRGen/CFG analysis). And if that isn't what isUnrecoverable() is referring to, we should define a new function which means that.

Okay, I think that is what `isUnrecoverable()` is addressing. Thank you! Just to double-check, then you're happy with the state of the patch as-is because use of `StmtError` will result in the function being marked as invalid and the diagnostic is not recoverable? Or are there changes you'd like to see @a-tarasyuk make?

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