If you know that the required versions are in your PATH, but this
script has made an error, then you can simply run
-autoreconf -I m4
+autoreconf -i -I m4
instead of this script.
## Let autoreconf figure out what, if anything, needs doing.
-autoreconf -I m4 || exit $?
+autoreconf -i -I m4 || exit $?
echo "You can now run \`./configure'."