upgade llvm? llvm10 is EOL

[motiejus]

Since llvm10 is EOL now (as of writing, only 11+ are available), can frawk update it's LLVM dependency, or perhaps document an easier way to find llvm10?

[ezrosent]

Thanks for pointing this out, and will do! I think LLVM 10 should still be fairly accessible and I will update the docs if I find updating to 12 will take too long. My hope is that updating to 12 should not be terribly difficult though. I'll try to follow up soon.

[ezrosent]

I've published frawk 0.4.4 on cargo, which now depends on LLVM 12