Fix tests runInit.node.ts failing on Windows (#1198)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/1198

Normalize paths so snapshots look the same on mac and win

Reviewed By: passy

Differential Revision: D21722773

fbshipit-source-id: 4a12117d3ec0fb57cdfc7c5bb06a5c0835412a5f

desktop/pkg/src/__tests__/runInit.node.ts

@@ -18,7 +18,7 @@ beforeEach(() => {
     // no implementation
   }
   function writeFile(name: string, contents: string) {
-    files[name] = contents;
+    files[name.replace(/\\/g, '/')] = contents;
   }
 
   files = {};