[clang] [Sema] Mark alias/ifunc targets used and consider mangled names (PR #87130)

[Fangrui Song via cfe-commits]

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@@ -0,0 +1,47 @@
+// RUN: %clang_cc1 -triple %itanium_abi_triple -Wunused -x c -verify %s
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MaskRay wrote:

I did `git mv alias-unused.c alias-unused.cpp`, but git does not preserve file move history...

Once the tests are in a good shape, I will pre-commit the file and change the PR to show the diff.

https://github.com/llvm/llvm-project/pull/87130