Disable TestCases/pthread_mutexattr_get on NetBSD
The pshared feature is unsupported on NetBSD as of today.
// RUN: %clangxx -O0 %s -o %t && %run %t
+// pthread_mutexattr_setpshared and pthread_mutexattr_getpshared unavailable
+// UNSUPPORTED: netbsd
+
#include <assert.h>
#include <pthread.h>
