[clang] [Clang] Add fake use emission to Clang with -fextend-lifetimes (PR #110102)

[Jeremy Morse via cfe-commits]

https://github.com/jmorse commented:

Tests are looking better (and github has helpfully thrown away most of my comments). I'll look at the code too now.

https://github.com/llvm/llvm-project/pull/110102