Switch JAVA_HOME to 21 for JRuby

common.js

@@ -403,3 +403,12 @@ export function setupPath(newPathEntries) {
   core.addPath(newPath.join(path.delimiter))
   return msys2Type
 }
+
+export function setupJavaHome() {
+  core.startGroup(`Modifying JAVA_HOME for JRuby`)
+  let newHomeVar = `JAVA_HOME_21_${os.arch().toUpperCase()}`;
+  let newHome = process.env[newHomeVar];
+  console.log(`Setting JAVA_HOME to ${newHomeVar} path ${newHome}`)
+  core.exportVariable("JAVA_HOME", newHome);
+  core.endGroup()
+}

ruby-builder.js

@@ -49,6 +49,10 @@ export async function install(platform, engine, version) {
   // Set the PATH now, so the MSYS2 'tar' is in Path on Windows
   common.setupPath([path.join(rubyPrefix, 'bin')])
 
+  if (engine == "jruby") {
+    common.setupJavaHome();
+  }
+
   if (!inToolCache) {
     await io.mkdirP(rubyPrefix)
     await downloadAndExtract(platform, engine, version, rubyPrefix)