libgo: use inline assembly in favor of call to _xgetbv()

Use inline assembly in the implementation of internal_cpu.xgetbv as
opposed to a call to the intrinsic _xgetbv(), since non-gcc compilers
(e.g. clang) may or may not have support for it.

Change-Id: If16289688529fdbcd8ba9d7339092521fe1abeda
Reviewed-on: https://go-review.googlesource.com/c/140137
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed