[clang] [DebugInfo] Add flag to only emit referenced member functions (PR #87018)

[Chris Davis via cfe-commits]

chrdavis wrote:

Building Chromium with this change shows a decrease of 35% for the PDB TPI size.  The TPI size is capped at 2GB due to a signed int limitation.  Since Chromium to approaching this limitation having this flag would be extremely beneficial.  Can we get this PR completed soon?

https://github.com/llvm/llvm-project/pull/87018