Suppress OSR for crossgen2 execution

[AndyAyersMS]

In CI testing, crossgen2 currently is run via a .NET 6 runtime, and
that runtime has some bugs in OSR.

Work around by suppressing OSR for the duration of the run. We should
be able to revert this once we update the crossgen2 runtime
to a .NET 7 version.

[AndyAyersMS]

cc @trylek @dotnet/jit-contrib

This should allow the jit-experimental CI legs to run cleanly.

[AndyAyersMS]

/azp run runtime-jit-experimental

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[trylek]

Looks great, thank you! These suppressions are a nasty hack that's likely to continue to bite us in the future, I'm wondering whether we might be able to devise some more robust scheme, I'll think about it during the holidays ;-).

[AndyAyersMS]

So far: one crossgen2 test doesn't use the normal execution path, so is still getting run and is failing for OSR: readytorun\multifolder. Will push a commit to try and fix that once the rest of the tests have finished.

[trylek]

Hmm, sorry about that one, I think that was originally created by me, it was supposed to exercise then new multi-component composite builds that are to this day beyond the scope of scripting used for "normal" CG2 tests.

[trylek]

In other words, if you end up having a hard time to make the test work, it shouldn't be a big deal to just disable it with an issues.targets entry and the core runtime team will tackle it as part of the .NET 7 feature work.

[AndyAyersMS]

It looks like it can get a similar fix -- it may end up disabling OSR for the running of the test as well, but that seems ok for now.

[AndyAyersMS]

That turned out to be the only issue remaining.

[MichalStrehovsky]

Looks great, thank you! These suppressions are a nasty hack that's likely to continue to bite us in the future, I'm wondering whether we might be able to devise some more robust scheme, I'll think about it during the holidays ;-).

Crossgen2 is one of the 1st party candidates for NativeAOT adoption in .NET 7. If we AOT compile crossgen2, these environment variables will no longer affect it. AOT compiling crossgen2 will also have other advantages based on my past experiments (#37411 (comment)).