Can't bootstrap if ninja is in the path

[refack]

ninja tries to run dukgyp but we're trying to build dukgyp 😵

D:\code\3party\dukgyp$ npm run build                                                      
                                                                                          
> [email protected] build D:\code\3party\dukgyp                                                
> gypkg build dukgyp.gyp.json                                                             
                                                                                          
ninja: Entering directory `out\Release'                                                   
ninja: error: 'dukgyp', needed by '../../bin/dukgyp', missing and no known rule to make it
child_process.js:524                                                                      
    throw err;                                                                            
    ^