[llvm] [llvm-gsymutil] Replace truncated DWARF names with mangled names from symbol table (PR #184221)

[Chen Li via llvm-commits]

================

----------------
thechenli wrote:

Done. Sort actually puts rich entries last (per the doc on FunctionInfo::operator<), so Prev is always non-rich and Curr is always rich in this branch — both the conditional RichFI/NonRichFI and the guarded swap collapse, leaving an unconditional swap to move the rich entry into FinalizedFuncs.back().

One fix needed to make this safe: the sort comparator didn't include CallSites, so a rich-via-CallSites-only entry could land before a non-rich one. Added CallSites.has_value() as a final tiebreaker in operator< so the invariant holds.

https://github.com/llvm/llvm-project/pull/184221