[clang] [Clang] Fix assertion when __block is used on global variables in C mode (PR #194856)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

> And I still have some doubts about @JustinStitt 's point of view, because I've observed that attributes like `__thread` don't mark themselves as invalid nodes after an error declaration, so I'm unsure if retaining `setInvalid` is a good practice.

I am not blocking on this and after reading Aaron's response I've become neutral -- I could see it either way. Feel free to ignore me :)


https://github.com/llvm/llvm-project/pull/194856