.github/workflows/mingw_linux: use a clean Ubuntu container for tests
.github/workflows/mingw_linux: use a clean Ubuntu container for tests

GitHub Actions worker now complains:

    Some packages could not be installed. This may mean that you have
    requested an impossible situation or if you are using the unstable
    distribution that some required packages have not yet been created
    or been moved out of Incoming.
    The following information may help to resolve the situation:

    The following packages have unmet dependencies:
     libwine:i386 : Depends: libfaudio0:i386 (>= 19.06.07) but it is not going to be installed
                    Depends: libglib2.0-0:i386 (>= 2.12.0) but it is not going to be installed
                    Depends: libgstreamer-plugins-base1.0-0:i386 (>= 1.0.0) but it is not going to be installed
                    Depends: libgstreamer1.0-0:i386 (>= 1.4.0) but it is not going to be installed
                    Recommends: libodbc1:i386 (>= 2.3.1) but it is not going to be installed
                    Recommends: gstreamer1.0-plugins-good:i386 but it is not going to be installed
    E: Unable to correct problems, you have held broken packages.

cf. https://github.com/fishilico/shared/runs/4616212560?check_suite_focus=true

Instead of battling instead the GitHub-provided virtual machine, use a
clean Ubuntu container image. This makes it possible to install Python
in Wine! And this requires having both 32-bit and 64-bit wine, so let's
do this.

fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared