[lld] [LLD] [MinGW] Hook up --icf=safe to -opt:safeicf (PR #70037)

[Zequan Wu via llvm-commits]

ZequanWu wrote:

Under safe ICF, it currently only checks Microsoft mangled vtable name. You may also want to update that as well to keep the behaviour consistent.
https://github.com/llvm/llvm-project/blob/8edcfa0d00de904558a700ccd250ddb073c6f1cd/lld/COFF/ICF.cpp#L96-L98

https://github.com/llvm/llvm-project/pull/70037