[clang] [clang][deps] NFC: Use qualified names for function definitions (PR #168586)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

@qiongsiwu Apologies for leading you down the wrong path in https://github.com/llvm/llvm-project/pull/161300#discussion_r2395304108.

https://github.com/llvm/llvm-project/pull/168586