[clang] [clang] Apply lvalue conversions to __builtin_classify_type argument (PR #175627)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

Apologies for the massive delay in reviewing this, it fell off my radar after standards meetings.

LGTM!

https://github.com/llvm/llvm-project/pull/175627