Modify compile scripts to grab ez80 LLVM compiler from its GitHub page instead of from a CEdev ZIP

[BlastBrothers]

This is the only thing we need the CEdev zip for currently. I almost went ahead and did this but the LLVM compiler page went down. Wouldn't be hard to implement once that's resolved. We could also just put the compiler files in this repo directly.

[astralaster]

Do you have a link to the LLVM compiler page?

[BlastBrothers]

Here

At some point recently the builds hosted here stopped being downloadable. The repo doesn't have regular releases so this is all there is, outside of building from source or grabbing them from the CEdev build... which builds them from source.

[sijnstra]

Would be nice to see at least the most recent version in the 15.0.x line being used. I have just managed to crash ez80-clang.