base-files: fix error message for /var/{run,lock} not being links

Closes: https://github.com/void-linux/void-packages/issues/36634

srcpkgs/base-files/INSTALL

@@ -38,8 +38,8 @@ make_system_dirs() {
 
 	# Create /var/run and /var/lock symlinks.
 	for d in run lock; do
-		if [ ! -h "var/$d" -a -d var/${d} ]; then
-			echo "/${d} must not be a directory, exiting!"
+		if [ ! -h "var/${d}" -a -d "var/${d}" ]; then
+			echo "/var/${d} must not be a directory, exiting!"
 			exit 1
 		fi
 	done