install_ide("newest") installs 1.8.11-ms-store-1 and linux build fails

[tobozo]

I was using this command in my travis.yml:

`install_ide '("newest")'`

and the build failed when arduino-ci-script tried to install 1.8.11-ms-store-1

https://travis-ci.org/tobozo/ESP32-Chimera-Core/builds/647062992

It was easily fixed by hardcoding the latest version but not that easy to spot as no error message is displayed whatsoever

[per1234]

Thanks so much for reporting this @tobozo! I'll make a fix and a release within the next few hours.