fix a bug in compiling with rtthread

include/fcntl.h

@@ -11,6 +11,8 @@
 #ifndef MLIBC_FCNTL_H__
 #define MLIBC_FCNTL_H__
 
+#include <sys/types.h>
+
 #define UNGET 8
 
 #define F_PERM 1

src/dummy/SConscript

@@ -0,0 +1,10 @@
+from building import *
+import os
+
+cwd     = GetCurrentDir()
+src     = Glob('*.c')
+CPPPATH = [cwd]
+
+group = DefineGroup('mlibc', src, depend = [''], CPPPATH = CPPPATH)
+
+Return('group')