[clang] [include-cleaner] Support multi-header symbols in mapping generator (PR #147720)

[kadir çetinkaya via cfe-commits]

https://github.com/kadircet requested changes to this pull request.

see https://github.com/llvm/llvm-project/pull/147720#discussion_r2250774590

https://github.com/llvm/llvm-project/pull/147720