[clang] [clang][Tooling] Fix assertion failure when processing CUDA files (PR #173762)

[Carlos Galvez via cfe-commits]

carlosgalvezp wrote:

For the record, it appears the reason I'm not hitting this assertion on my side is because my clang-tidy build is with assertions disabled... :flushed: It still does exactly what I want (run clang-tidy on both host and device in one invocation). It would be great to support this without having to run 2 invocations.

https://github.com/llvm/llvm-project/pull/173762