- Base container: Fedora 32
- Mono uses version 6.12.0.102, MSBuild 16.6
- Linux builds use GCC 9
- Windows builds use Fedora 32's mingw-gcc (GCC 9)
- JavaScript uses Emscripten 1.39.9 (Mono 6.12 requires 1.39.7 but that version
fails generating .wasm, so we backport a patch to get 1.39.9)
- Install SCons 4.0.1 from pip
This saves us from pulling gtk2 and gtk3 as weak deps of
perl and git or whatnot... And we don't need to pull in all
the documentation on Ubuntu.
Also ensures that we properly run `dnf clean all` after each
installation.