We don't have this include.

Index: runtime/flangrti/mpmalloc.c
--- runtime/flangrti/mpmalloc.c.orig
+++ runtime/flangrti/mpmalloc.c
@@ -7,7 +7,7 @@
 
 /* mp-safe wrappers for malloc, etc. */
 
-#ifdef TARGET_LINUX
+#if defined(TARGET_LINUX) && !defined(__OpenBSD__)
 #include <features.h>
 #endif
 
