build-sys: use set +e before patch --try in ./autogen.sh

Addresses: https://github.com/karelzak/util-linux/issues/1476
Signed-off-by: Karel Zak <kzak@redhat.com>

autogen.sh

@@ -134,10 +134,12 @@ if test -f tools/libtool.m4.patch; then
 		rm m4/libtool.m4
 		mv m4/libtool.m4.org m4/libtool.m4
 	fi
+	set +e
 	patch --batch --dry -p1 < tools/libtool.m4.patch > /dev/null 2>&1
 	if [ "$?" -eq 0 ]; then
 		patch -p1 --batch < tools/libtool.m4.patch
 	fi
+	set -e
 fi
 
 aclocal -I m4 $AL_OPTS