[Linkage] COMDAT

Reference:
https://maskray.me/blog/2021-07-25-comdat-and-section-group

COMDAT gives indication to the linker to deduplicate the inline/weak reference/external linkage symbols.

https://github.com/llvm/llvm-project/blob/2e603c6/clang/lib/AST/ItaniumMangle.cpp#L1458-L1472

inline vs. non-inline name mangling with extra letter 'L'.

e.g.

_ZSt8in_place vs. _ZStL8in_place