The in-container build scripts now get passed CLASSICAL and MONO env
variables which can be used to build one or the other, or both
(default).
`build.sh`, `build-release.sh` and `build-templates.sh` now all expect
command line switches to specify the version details, and optionally
which flavor to build.
For example to build Mono only:
./build.sh -v 3.2-beta4 -g master -b mono
./build-release.sh -v 3.2-beta4 -b mono
./build-templates.sh -v 3.2-beta4 -t 3.2.beta4 -b mono
Also took the opportunity to do some extra cleanup, like removing
unnecessary `builtin_*` options since they all default to True, even
for Linux in 3.2, as well as `use_lto` and `use_static_cpp` options
on platforms which don't implement them.
And I improved the `build-release.sh` script to be a bit easier to
read, and avoid having too many stray folders to cleanup.
The build scripts should now generate the final structure that we'd use
on the official mirrors, with the `mono` distribution as a subfolder of
the main release folder.
- Add Mono builds for Android.
- Remove now unused `MONO*_PREFIX` env variables (replaced by `mono_prefix`
command line option).
- Update iOS to SDK 12.4 and darwin17 for proper ARKit support.
- Drop 32-bit support for iOS (armv7, x86).
