I just tested “yarn run build”, it won’t run. I believe it should be:
“yarn electron-builder build .” (without quotes).
edit: Electron-builder appears to have also added some more modules, the installer has increased to about +10 meg in size. I hope they don’t go nuts like electron-packager. fingers crossed
For some reason, the “yarn run build” is working for me, but I tested the “yarn electron-builder build” command which works and is better in my opinion, since it calls electron builder explicitly. Thanks for the suggestion 
When ever I enter the words “npx build .” (i typed it without quotes btw), it produces these errors:
npm ERR! could not determine executable to run
npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\passi\AppData\Local\npm-cache_logs\2021-03-13T20_51_18_013Z-debug.log
This maybe helps you, take a look there is a simple guide to achive a Windows build
https://www.gamesigniter.com/build-your-gdevelop-5-game-with-yarn-electron-builder/
Hello! Ulises post above is correct. This thread is old info.
In general, please don’t bump two year old threads. If you have something similar to this instance in the future, rather than bump a stale post over 12 months old, I would recommend making a new post that links or references the original.
Closing this thread out since it is no longer relevant.