Adds support for building Mono templates for Android in 3.2/master.
We use the script from https://github.com/godotengine/godot-mono-builds
to build Mono for all arches with the right options, and a patch included
from https://github.com/godotengine/godot/blob/master/modules/mono/build_scripts/patches/fix-mono-android-tkill.diff
which is also necessary.
I also moved the SDK to a `sdk` folder to make the `$HOME` more tidy,
especially since the Mono build scripts install the mono toolchains in
`$HOME` too by default.
Using a git clone for specific mono version tag, as the upstream tarballs
are iffy (the 5.18.1.3 tarball lacks files needed to build on Android).
Install xz/xz-utils and conditionally handle tar.xz tarballs from 6.0+.
On Windows, I ran into a build issue due to `make distclean` being
bogus in 6.0.0.319 (mono/mono#16605), so I worked it around by starting
from a clean folder for each build.
The hotfixed mingw-binutils packages should likely be rebuilt against
Fedora 30's mingw-binutils, but I didn't find the src.rpm in the repo
to do it. There were no functional changes between F29 and F30's
mingw-binutils though, so we should be fine as is:
https://src.fedoraproject.org/rpms/mingw-binutils/commits/f30
The `MONO32_PREFIX` and `MONO64_PREFIX` are no longer used by the
buildsystem (replaced by a `mono_prefix` build option), but I kept them
where relevant to point to non-standard install locations.
* 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.