makepkg: add rw permissions to /pkg directory on fail

after step failed(makepkg failed to build the package), user shouldn't need root
permissions to view/remove the directory

see: https://bugs.archlinux.org/task/50439

scripts/makepkg.sh.in

@@ -369,6 +369,10 @@ error_function() {
 		error "$(gettext "A failure occurred in %s().")" "$1"
 		plainerr "$(gettext "Aborting...")"
 	fi
+	# in case /pkg directory doesn't have rw permissions
+	if [[ -d "$pkgdirbase" ]]; then
+		chmod 755 "$pkgdirbase"
+	fi
 	exit $E_USER_FUNCTION_FAILED
 }