iOS image is now based on the OSX one, as we'll need the OSX
toolchain to build the AOT cross-compiler.
We can't build the cross-compiler yet though as godot-mono-builds
doesn't support OSXCross for that part, and we will likely need
to build libclang manually beforehand too.
The previous `['/bin/bash']` was not working, running the image
with `podman run -it <name>` would evaluate to:
```
> sh -c ['/bin/bash']
sh: [/bin/bash]: No such file or directory
```
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.
* Mono config on MacOSX is not portable from the Linux and Windows
version.
* Rename the compilers so that 'gcc' and 'g++' are the new version by
default.
* Add default environment variables to containers.
Rémi Verschelde
Cory Petkovsek
Rémi Verschelde
Hein-Pieter van Braam-Stewart