gallium: Don't pass avx512er and avx512pf features on LLVM 19
gallium: Don't pass avx512er and avx512pf features on LLVM 19
These target features have been remove in LLVM 19, and cause warnings like the following to be printed:
'-avx512er' is not a recognized feature for this target (ignoring feature)
'-avx512pf' is not a recognized feature for this target (ignoring feature)
Do not pass these target features on LLVM 19 and newer.
Fixes #11870 (closed).