Problem seems to have been solved! Not sure exactly what solved it -- maybe I fixed a build script earlier, or maybe it's because some of the libraries I used to build today are only weeks old releases.
I verify that gspawn-win32-helper.exe ends up in my build folder, and when I install and run the final package, I am able to open two notebooks using File -> Open.
Problem seems to have been solved! Not sure exactly what solved it -- maybe I fixed a build script earlier, or maybe it's because some of the libraries I used to build today are only weeks old releases.
I verify that gspawn- win32-helper. exe ends up in my build folder, and when I install and run the final package, I am able to open two notebooks using File -> Open.