Fix race conditions in CG2 runs (#44492)

Fix race conditions in CG2 runs (#44492)

While we do lock the test folder during CG2 compilation, we always
run the compilation which means that it can race with execution of
the already CG2-compiled executable which also locks the PE file.

While I'm not super happy about introducing more state, I believe
the easiest way to fix this is the same way CG1 works - compiling
opportunistically upon first build of the project and skipping the
compilation subsequently.

Thanks

Tomas