[OpenMP] fix asm code for for arm64 (AARCH64) for Darwin/macOS

Adjusted external reference for Darwin/AARCH64 link compatibility.
Made size directive conditional only if __ELF__ defined.

Patch by Michael_Pique <mpique@icloud.com>

Differential Revision: https://reviews.llvm.org/D88252

GitOrigin-RevId: 7b5254223acbf2ef9cd278070c5a84ab278d7e5f
1 file changed