Add warning for GitHub runners

Author: 0x2b3bfa0

src/drivers/github.js

@@ -251,7 +251,9 @@ class Github {
 
   async startRunner(opts) {
     const { workdir, single, name, labels, env } = opts;
-
+    
+    this.warn('cloud credentials are no longer available on self-hosted runner steps; please use step.env and secrets instead');
+    
     try {
       const runnerCfg = resolve(workdir, '.runner');