Don't compile programs using fork() on MMU-less systems

Systems that lack a MMU cannot use fork() to create the child process.
The patch does not compile the affected programs on MMU-less systems.

Co-developed-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

check_cc.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+# check_cc.sh - Helper to test userspace compilation support
+# Copyright (c) 2015 Andrew Lutomirski
+
+CC="$1"
+TESTPROG="$2"
+shift 2
+
+if [ -n "$CC" ] && $CC -o /dev/null "$TESTPROG" -O0 "$@"; then
+    echo 1
+else
+    echo 0
+fi
+
+exit 0