Setting up the box itself is not really the problem, I've done that plenty of times with various VM/OS combinations. Right now I use a console-only Debian, I basically want something super light and I don't need a UI.
I was more talking about the source tree set up. What I want is to have the Git repo checked out on the host only (not on the VM) and the VM can access its directory tree and run the tests against it. Not sure in your explanation if you do something like that or if you have a repo on both sides and push/pull between them or something. For now I could obtain what I wanted using rsync, with bin.v2 directory excluded from the sync.
As for Mingw, it's precisely to move off it that I'm doing that. It fails too many tests, most notably with the famous "too many sections" error. I want to go native GCC. I work on my work computer while commuting, and it's on Windows unfortunately.