Assuming Ronin is downloaded and extracted to ~/Downloads/ronin-main
See https://github.com/MacGapProject/MacGap1 for details

sudo gem install macgap
mkdir ~/tmp
cd ~/tmp
macgap new Ronin
cp ~/Downloads/ronin-main/index.html Ronin/
macgap build Ronin
open ./Ronin.app

thanks.  worked great with Ronin.  

The menu bar seems upside down, any known fixes?

I just used this process to build an app for Dotgrid, but am seeing the same upside-down menu bar. would love to know of any possible fixes!

edit: weirdly, resizing the window bar when trying to get a screenshot of the issue made it go to the correct place at the top of the screen?? good news, I guess! though it seems I have to do this each time I open the app.