If you want to test generated files, the right way is for someone to install the PSDK on Windows, generate files with midl, and use that as test sources, similar to the existing generated.c files.
FWIW there's several checks failing in several of these files when I try to build them with the latest MSVC version https://gcc.godbolt.org has (v19.32). Arguably some of these failures are caused by the addition of new struct members, but there's also some type alignment mismatch, some unknown types and some misnamed fields. I think it's still a sign that not routinely testing these things and using manually generated files makes it not very reliable and tends to rot.
Then it indeed means that the testbot needs to have the PSDK and build tools installed on some VMs, updated from time to time (and it raises a question to how to handle SDK versions, but at least one official version would be good), and that the tests should probably be changed to compile them with MSVC during the test. I think that having all this would also make public header changes validation easier.