libc: Add pthread_attr_get_np(3) stub, reporting ESRCH.

This seems to be required by recent clang asan.
I do not see other way than put the symbol under FBSD_1.0 version.

PR: 251112
Reported by: Andrew Stitcher <astitcher@apache.org>
Reviewed by: emaste
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D27389