[clang] [clang][analyzer] Fix alpha.unix.BlockInCriticalSection for CTU (PR #90030)

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gamesh411 wrote:

After reducing a crashing TU, I have found, that the issue came up without CTU analysis as well.
I have added a test case that demonstrates the crash without the fix.
I also updated the commit message to reflect the real cause.

https://github.com/llvm/llvm-project/pull/90030