use weak to fix f.e. cdrkit static compile. fixes #3

libc/sysdeps/linux/common/setreuid.c

@@ -37,4 +37,4 @@ int setreuid(uid_t ruid, uid_t euid)
 }
 #endif
 
-libc_hidden_def(setreuid)
+libc_hidden_weak(setreuid)