Restore dynamic-compile (JIT) functionality with LLVM 12+

[kinke]

By completing #3184, the transition to the ORCv2 API.

[cpaelzer]

Hi,
this also affects Ubuntu which - for now - can revert to build with llvm-11, but one can't predict when Distributions start to remove the older llvm toolchains.

Therefore I wanted to kindly ask if there is any progress here as the former #3184 seems to have stalled for the last two years.

[Hardcode84]

Sorry, I don't have time to support this now. This JIT work was done as experiment and for my personal projects (none of them developed enough to be useful). I am not aware if anyone else besides me actually uses it. Best way forward would be probably to disable JIT support via cmake option.

[kinke]

Best way forward would be probably to disable JIT support via cmake option.

[That's the status quo, disabled by default for LLVM 12+.]

[cpaelzer]

Thank you for your guidance on this topic @Hardcode84 !
I'll - for now - build it in Ubuntu with llvm-11 to overcome the issue temporarily but suggest to Debian that disabling it seems to be the way forward as it was an experimental personal project.
Once Debian agrees we (Debian+Ubuntu+other Derivatives) can go that path together then (including potential changes to dependencies).