Update MinGW CI to Ubuntu 20.04 * Use ghcr.io/lmms/linux.mingw:20.04 * Fix deprecation in ClipView.cpp * Fix ccache and simplify git configuration * Apply patch by @DomClark for MinGW's SDL2 target * Update excludelist-win
Update MinGW CI to Ubuntu 20.04 * Use ghcr.io/lmms/linux.mingw:20.04 * Fix deprecation in ClipView.cpp * Fix ccache and simplify git configuration * Apply patch by @DomClark for MinGW's SDL2 target * Update excludelist-win