[clang] Add sincos builtin using `llvm.sincos` intrinsic (#114086)
This registers `sincos[f|l]` as a clang builtin and updates GCBuiltin to
emit the `llvm.sincos.*` intrinsic when `-fno-math-errno` is set. Note:
`llvm.sincos.*` is only emitted by `__builtin_sincos[f|l]` functions in
this initial patch.