[clang] [Clang] Fix crash with `source_location` in lambda declarators. (PR #107411)

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cor3ntin wrote:

> While looking at it, I found another bug where we seem to have problems mangling `std::source_location` https://clang.godbolt.org/z/467E19h45

See https://github.com/llvm/llvm-project/issues/59948#issuecomment-2331676234 :) 

https://github.com/llvm/llvm-project/pull/107411