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

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

I don't think we want to use the "isInvalidDecl" bit here.  The declaration is still valid in the sense that code referring to the declaration should treat it normally.  (For example, we want overload resolution to work the same way it usually does.)

One way to think of this is that we're essentially inferring __device__ markings for functions that can't be built on the host.  Then if it turns out we actually need the function on the host, we error out because you're trying to use a function that isn't available.

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