Update buildscript

.github/scripts/update_version

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+if ! git diff --name-only HEAD HEAD~1 | grep -qF 'build.gradle'; then
+  new_version="$(date +%s)"
+  sed --in-place "s!^//version:.*!//version: $new_version!g" build.gradle
+  git add build.gradle
+  git commit -m "[ci skip] update build script version to $new_version"
+  git push
+  printf 'Updated buildscript version to %s\n' "$new_version"
+else
+  printf 'Ignored buildscript version update: no changes detected\n'
+fi