Only upcase x64 platform

The JAVA_HOME_* variables use 'arm64' on ARM.

Author: headius

common.js

@@ -406,7 +406,11 @@ export function setupPath(newPathEntries) {
 
 export function setupJavaHome() {
   core.startGroup(`Modifying JAVA_HOME for JRuby`)
-  let newHomeVar = `JAVA_HOME_21_${os.arch().toUpperCase()}`;
+  let arch = os.arch().toUpperCase();
+  if (arch == "x64") {
+    arch = "X64"
+  }
+  let newHomeVar = `JAVA_HOME_21_${arch}`;
   let newHome = process.env[newHomeVar];
   console.log(`Setting JAVA_HOME to ${newHomeVar} path ${newHome}`)
   core.exportVariable("JAVA_HOME", newHome);