no target nwjs when build nw on nw14 branch

[nintyzcy]

i want to build nw of v0.14.7 for window xp use. so i listen the document of https://nwjs-docs.readthedocs.io/en/latest/For%20Developers/Building%20NW.js/.

1. gclient config --name=src https://github.com/nwjs/chromium.src.git@origin/nw14. then modify .gclient file.
2. gclient sync --with_branch_heads. get code success
   3.Manually clone and checkout v0.14.7 branch for following repositories:
   src/content/nw | https://github.com/nwjs/nw.js
   src/third_party/node-nw | https://github.com/nwjs/node
   src/v8 | https://github.com/nwjs/v8
3. gn gen out/nw. success
4. ninja -C out/nw nwjs. failed!
   ninja: error: unknown target 'nwjs', did you mean 'nfc'?

I opened out/nw/build.ninja, actually not found nwjs. am i need to modify src/BUILD.gn，and how to do? I found that
the project nwjs/nw.js at branch of nw14, still use gyp not gn to build. does it matter?