We should look into changing this setting, so that we build on all PRs. This helps us verify changes in build.ps1 more easily.

The easiest way to fix this from what I can tell would be to tweak this part to set the NuGet package version like this, unless $env:APPVEYOR_REPO_TAG -eq "True"

(In other words, we will get junk version numbers like 62.0.0-CI34 until we tag the repo; for these builds, we will set the NuGet package version to match the tag just like we've done historically.)

Anyone wants to fix this - feel free, it's up for grabs.