Define pthread_attr_getstacksize/setstacksize

Bug: aomedia:2754, aomedia:3567
Change-Id: I54d9e3e8c1253c9cd9624b3732f4ec0a69d76529

aom_util/aom_thread.h

diff --git a/aom_util/aom_thread.h b/aom_util/aom_thread.h
index ec2ea43..0e469c0 100644
--- a/aom_util/aom_thread.h
+++ b/aom_util/aom_thread.h
@@ -71,6 +71,20 @@
   return 0;
 }
 
+static INLINE int pthread_attr_getstacksize(const pthread_attr_t *attr,
+                                            size_t *stacksize) {
+  (void)attr;
+  (void)stacksize;
+  return EINVAL;
+}
+
+static INLINE int pthread_attr_setstacksize(pthread_attr_t *attr,
+                                            size_t stacksize) {
+  (void)attr;
+  (void)stacksize;
+  return EINVAL;
+}
+
 static INLINE int pthread_create(pthread_t *const thread,
                                  const pthread_attr_t *attr,
                                  unsigned int(__stdcall *start)(void *),