taken from lang/mruby

Index: mruby/include/mrbconf.h
--- mruby/include/mrbconf.h.orig
+++ mruby/include/mrbconf.h
@@ -7,6 +7,7 @@
 #ifndef MRUBYCONF_H
 #define MRUBYCONF_H
 
+#include <endian.h>
 #include <limits.h>
 #include <stdint.h>