We've had a break #6289 that was fixed with #6301.

However long term I'd like to rationalize the following:

1. why are we dynamically loading the assembly there in the first place? Is this the right thing to do?
2. can we more closely replicate what happens in the actual production VS? Since NuGet.Frameworks.dll there is loaded from a single location (not next to MSBuild.exe), but in bootstrap it is deployed to two separate locations and loaded from both, which seems fragile and caused the above issue.