[clang] Fix enum enumerator visibility loss when #include is between module imports (PR #188865)

[Avi Kivity via cfe-commits]

avikivity wrote:

> > Clang 22.1.1 (unpatched) also does not reject the redefinition. The patch does not cause a regression, and it is yet another bug.
> 
> @avikivity Are you sure? I didn't check that specific version, but both 22.1.0 and trunk diagnose the redefinition: https://godbolt.org/z/qPY7Ea3r5

I'm not sure of anything. But [redef.zip](https://github.com/user-attachments/files/26346274/redef.zip) reproduces the bug on clang 21.1.1 (from Fedora rawhide).


https://github.com/llvm/llvm-project/pull/188865