Hmm that solution ended up rebuilding LLVM every time, try this instead
WIP: AST Interpreter
Bash the existing OSR code into submission for the new AST interpreter

Once we get the AST interpreter in, we can add resume-from-any-point
functionality, which means that we can get rid of the current OSR system.
Maybe we should have done that first, but I thought it would be easy
to get the OSR stuff working.
wip