Define pthread_attr_getstacksize/setstacksize

Bug: aomedia:2754, aomedia:3567
Change-Id: I0608ffe8f0e6fc2f99f8834408084308e51aaf3e

aom_util/aom_pthread.h

diff --git a/aom_util/aom_pthread.h b/aom_util/aom_pthread.h
index 1a97a0a..425a6b0 100644
--- a/aom_util/aom_pthread.h
+++ b/aom_util/aom_pthread.h
@@ -72,6 +72,20 @@
   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 *),