Fix build on windows

Summary: Fix for build on windows

Reviewed By: mweststrate

Differential Revision: D20601309

fbshipit-source-id: 9845964513d7904f58e3511b1c4daa8716f7b054

desktop/static/get-watch-folders.ts

@@ -29,10 +29,11 @@ export default async (packageDir: string) => {
         }
       }
     }
-    if (packageDir === '/') {
+    const nextDir = path.dirname(packageDir);
+    if (!nextDir || nextDir === '/' || nextDir === packageDir) {
       break;
     }
-    packageDir = path.dirname(packageDir);
+    packageDir = nextDir;
   }
   return watchDirs;
 };