Provide standalone clang 8 project usable across all platforms
We plan to ship to clang 8 where a clang is needed in Firefox 68. We should create a separate project for it and retire the llvm one we have later on as the consensus seems to be to use "clang" instead of "llvm". This ticket is motivated as well by comment:43:ticket:28716.
To upload designs, you'll need to enable LFS and have admin enable hashed storage. More information