KVM: selftests: Use __GLIBC__, not _GNU_SOURCE, to detect actual glibc

Use __GLIBC__ in the hardware disable test to detect when selftests are
being built/linked against glibc and thus pthread_attr_setaffinity_np() is
(hopefully) available.  As pointed out by Sashiko and Hisam, _GNU_SOURCE is
effectively a "request" macro to enable functionality, whereas __GLIBC__ is
an announcement of support and selftests' idiomatic way of guarding code
that's specific to glibc.

Fixes: 496779b54943 ("KVM: selftests: Pre-set threads affinity in hardware disable test when possible")
Reported-by: Sashiko Bot <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260731201140.5AF0C1F00AC4@smtp.kernel.org
Suggested-by: Hisam Mehboob <hisamshar@gmail.com>
Link: https://patch.msgid.link/20260826161430.714316-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions