We force using Emscripten 1.38.47 as there is a regression in 1.38.48
and 1.39.x which makes the generation of our .wasm file fail.
Up until now we used the desktop BCL (compiled with desktop Mono)
for both desktop and Android, but that does not work for WebAssembly
(and we suspect Android issues related to it).
So we now build the Android and WebAssembly BCLs in the relevant
containers, which are later copied in the templates directory to
include on export. We already have the desktop BCL from the regular
build.
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).