Abort on not fully provisioned buildserver VM
Recently it happened apparently multiple times that the build VM wasn't fully provisioned and nearly all builds failed subsequently.
We can detect this by checking for an existing buildserverid file first and if that's not present abort the whole fdroid build --all
process.
This hopefully will lead to far less confusing errors for misteriously failing app builds. It also ensures we are always building within the expected environment.
@eighthave @uniqx @relan thoughts?
Edited by Marcus