tools/nolibc: open: fix up compile warning for arm

In function ‘open’:
nolibc/sysroot/arm/include/sys.h:919:23: warning: ‘mode_t’ {aka ‘short unsigned int’} is promoted to ‘int’ when passed through ‘...’
919 | mode = va_arg(args, mode_t);
| ^
nolibc/sysroot/arm/include/sys.h:919:23: note: (so you should pass ‘int’ not ‘mode_t’ {aka ‘short unsigned int’} to ‘va_arg’)
nolibc/sysroot/arm/include/sys.h:919:23: note: if this code is reached, the program will abort

Signed-off-by: Zhangjin Wu <[e-mail]>
Reviewed-by: Thomas Weißschuh <[e-mail]>
Signed-off-by: Willy Tarreau <[e-mail]>
Signed-off-by: Paul E. McKenney <[e-mail]>

tools/include/nolibc/sys.h

···
 		va_list args;
 
 		va_start(args, flags);
-		mode = va_arg(args, mode_t);
+		mode = va_arg(args, int);
 		va_end(args);
 	}