[clang] [clang][CodeGen] Fix in codegen for __builtin_popcountg/ctzg/clzg (PR #90845)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Please add a testcase for i1/i2 (which are the only cases where this actually matters).

https://github.com/llvm/llvm-project/pull/90845