include sys/mount.h for everyone

libc/sysdeps/linux/common/umount.c

@@ -8,11 +8,11 @@
  */
 
 #include "syscalls.h"
+#include <sys/mount.h>
 
 /* arch provides umount() syscall */
 #ifdef __NR_umount
 
-# include <sys/mount.h>
 _syscall1(int, umount, const char *, specialfile);
 
 /* arch provides umount2() syscall */