I just had a random thought: perhaps it would be a good idea to have a project that doesn't do optimizations, but just focuses on fast compiling.

Then again, I now can't help but wonder if LLVM (or even GCC) would be fast, if you just turned off all the optimizations ...

(Of course, at this point, I can't help but think "you don't need to worry about the speed of compilation" in things like Common Lisp or Smalltalk, because everything is compiled incrementally and immediately, so you don't have to wait for the entire project to compile before you could test something ...)