Correctly reference cwd instead of __dirname

Summary:
This is for issue #7670.  I consider this a typo, but maybe you don't.

In order to see the problem, you need to have the packager search for the configuration in a place that doesn't have one and the default configuration can't be provided.  It's likely that no one is doing this and also why this probably wasn't seen.
Closes https://github.com/facebook/react-native/pull/7671

Differential Revision: D3350412

fbshipit-source-id: 5f9b520f7d5cbc749e2b898e7bbf2cd84d81ace0

local-cli/util/Config.js

@@ -33,7 +33,7 @@ const Config = {
     const parentDir = findParentDirectory(cwd, RN_CLI_CONFIG);
     if (!parentDir && !defaultConfig) {
       throw new Error(
-        `Can't find "rn-cli.config.js" file in any parent folder of "${__dirname}"`
+        `Can't find "rn-cli.config.js" file in any parent folder of "${cwd}"`
       );
     }