Clarify Windows check

Author: eregon

dist/index.js

@@ -39,7 +39,7 @@ export async function setupRuby(options = {}) {
   const [engine, parsedVersion] = parseRubyEngineAndVersion(inputs['ruby-version'])
 
   let installer
-  if (platform === 'windows-latest' && engine === 'ruby') {
+  if (platform.startsWith('windows-') && engine === 'ruby') {
     installer = require('./windows')
   } else {
     installer = require('./ruby-builder')