There are a few different things here.
- fundamental issues in SILOptimizer that prevented the build the last I tried (granted this was a while ago).
- incorrect dependencies for the targets / other issues in the custom build system
- the dependency on Swift is a problem for the official builds
So, even if the technical blockers are resolved, we will not be able to enable the support in the nightlies as the toolchain is far too large and installing the Swift toolchain means that we do not have sufficient space to build just the compilers even (though this will require building the runtime and all so it will require even more space).
The first step towards this would be to get the SILOptimizer bugs fixed as they are preventing the code from compiling even.