As part of the switch-over from Crossgen1 to Crossgen2 we should start running regular library test runs over CG2-compiled framework to catch potential regressions or issues. We should update the library test build scripts to optionally support CG2 compilation of framework assemblies, add the corresponding support to the YAML scripts and define a new type of run leveraging this functionality to run library tests over CG2-compiled framework. For now I would run them on a daily basis; if they turn out to be stable enough, we may consider switching some of the library tests in PR runs to work this this too.

/cc @dotnet/runtime-infrastructure, @dotnet/crossgen-contrib