fix signed left-shift overflow in pthread_condattr_setpshared

src/thread/pthread_condattr_setpshared.c

@@ -4,6 +4,6 @@ int pthread_condattr_setpshared(pthread_condattr_t *a, int pshared)
 {
 	if (pshared > 1U) return EINVAL;
 	a->__attr &= 0x7fffffff;
-	a->__attr |= pshared<<31;
+	a->__attr |= (unsigned)pshared<<31;
 	return 0;
 }