Prepare release v312 (heroku#1612)

Co-authored-by: heroku-linguist[bot] <136119646+heroku-linguist[bot]@users.noreply.github.com>

Author: heroku-linguist[bot]

CHANGELOG.md

@@ -3,6 +3,11 @@
 ## [Unreleased]
 
 
+## [v312] - 2025-06-10
+
+- JRuby 9.4.13.0 is now available
+
+
 ## [v311] - 2025-06-09
 
 
@@ -1716,7 +1721,8 @@ Bugfixes:
 * Change gem detection to use lockfile parser
 * use `$RACK_ENV` when thin is detected for rack apps
 
-[unreleased]: https://github.com/heroku/heroku-buildpack-ruby/compare/v311...main
+[unreleased]: https://github.com/heroku/heroku-buildpack-ruby/compare/v312...main
+[v312]: https://github.com/heroku/heroku-buildpack-ruby/compare/v311...v312
 [v311]: https://github.com/heroku/heroku-buildpack-ruby/compare/v310...v311
 [v310]: https://github.com/heroku/heroku-buildpack-ruby/compare/v309...v310
 [v309]: https://github.com/heroku/heroku-buildpack-ruby/compare/v308...v309

lib/language_pack/version.rb

@@ -2,6 +2,6 @@
 
 module LanguagePack
   class LanguagePack::Base
-    BUILDPACK_VERSION = "v311"
+    BUILDPACK_VERSION = "v312"
   end
 end