Install Crystal on Mac M1

[maxfierke]

The blog post from my earlier post has been updated to reference LLVM 11 specifically and address the initial cloning of the source code. I would caution against building with LLVM 12 at this time, as Beta reminded me in another post it does not contain a vital patch that Homebrew’s LLVM 11 has that ensures release mode builds still function correctly. The patch only exists in LLVM master (and will likely be included in LLVM 13) but is not applied to LLVM 12 in Homebrew or elsewhere, as far as I know.