scripts: fix tools override

The tools found by the new autostuff configure can contain arguments,
for example: grep -E

This needs separating the paths set for the Makfile from the paths
set for the scripts.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

#!/bin/sh

set -e

printf "Running autoconf...\n"

autoconf -Wall --force

printf "Done. You may now run:\n    ./configure\n"