Fix designer build on windows

     [exec] > nuxeo-view-designer@ lint C:\dev\projects\nuxeo-studio\nuxeo-view-designer
     [exec] > ./node_modules/gulp/bin/gulp.js lint && ./node_m'.' n'est pas reconnu en tant que commande interne
     [exec] ou externe, un programme exécutable ou un fichier de commandes.
     [exec] npm ERR! coodules/polymer-cli/bin/polymer.js lint -i elements/*/*.html
     [exec]
     [exec] de ELIFECYCLE
     [exec] npm ERR! errno 1
     [exec] npm ERR! nuxeo-view-designer@ lint: `./node_modules/gulp/bin/gulp.js lint && ./node_modules/polymer-cli/bin/polymer.js lint -i elements/*/*.html`
     [exec] npm ERR! Exit status 1
     [exec] npm ERR!
     [exec] npm ERR! Failed at the nuxeo-view-designer@ lint script.
     [exec] npm ERR! This is probably not a problem with npm. There is likely additional logging output above.