I'm sure whoever ends up packaging this would check out the latest release, but just in case, the latest release as of today is 0.23.1.

The problem with packaging Crystal is that it doesn't have a bootstrap; Crystal requires Crystal to compile. The solution to this, I guess, is to fetch the distributed binary for use in building, but I don't know if we encourage that in situations like this. Do we have a precedence?

Go is the closest I can find, and it correctly has golang as a build dep. Do we just fudge the very first build and leave it for the build bot to figure it out?

edit: Attempting to package it, and it seems that llvm-config --cxxflags generates flags that aren't recognised by our version of g++:

x86_64-solus-linux-g++ -c -mtune=generic -march=x86-64 -g2 -O2 -pipe -fPIC -fno-omit-frame-pointer -fexceptions -D_FORTIFY_SOURCE=2 -fstack-protector --param ssp-buffer-size=32 -fasynchronous-unwind-tables -ftree-vectorize -feliminate-unused-debug-types -Wall -Wno-error -Wp,-D_REENTRANT  -o src/llvm/ext/llvm_ext.o src/llvm/ext/llvm_ext.cc `/usr/bin/llvm-config --cxxflags`
x86_64-solus-linux-g++: error: unrecognized command line option '-Wcovered-switch-default'; did you mean '-Wno-switch-default'?
x86_64-solus-linux-g++: error: unrecognized command line option '-Wstring-conversion'; did you mean '-Wint-conversion'

It's pretty common for languages to self-host. It's really convenient for the language developers but it can be pretty annoying for everyone else if there's no provided bootstrap or when trying to build for a new target triple.

Is there anything I can help with?

They figured it out eventually, just never fixed their patches. This is waiting for a maintainer to step forward.