add static_assert define missing on < 10.11 SDK

fixes C11 code that uses static_assert

include/assert.h

@@ -0,0 +1,22 @@
+
+/* Include the primary system assert.h */
+#include_next <assert.h>
+
+
+/* now add the missing definition of static_assert for C11 code */
+/* this was added to the 10.11 SDK, but we can't easily check for that, so we use ENV_MIN_REQUIRED instead */
+
+#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && ((__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__-0) < 101100)
+
+#ifndef _ASSERT_H_
+#define _ASSERT_H_
+
+#ifndef __cplusplus
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define static_assert _Static_assert
+#endif /* __STDC_VERSION__ */
+#endif /* !__cplusplus */
+
+#endif /* _ASSERT_H_ */
+
+#endif /* __ENVIRONEMENT */