[clang] [Clang] Fix assertion when __block is used on global variables in C mode (PR #183988)

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TPPPP72 wrote:

@nico This wasn't an intentional change, but it seems my code modification has indeed caused some side effects. I suspect it might be because my check on `hasLocalStorage()` was too aggressive. I'll fix it as soon as I find the specific cause.

https://github.com/llvm/llvm-project/pull/183988