-git submodule update --init || echo "Failed to update Gnulib sources from git."
-if test -x ./gnulib/gnulib-tool; then
- ./gnulib/gnulib-tool --update -S || die "Failed to update Gnulib."
+: ${AUTORECONF=autoreconf}
+: ${GNULIB=gnulib}
+: ${GIT=git}
+: ${PERL=perl}
+
+$GIT submodule update --init \
+ || echo "Failed to update Gnulib sources from git."
+
+if test -x $GNULIB/gnulib-tool; then
+ $GNULIB/gnulib-tool --update -S || die "Failed to update Gnulib."