Generate the module inside the repl

The Kaleidoscope tutorial acts as a repl where each top-level expression
is evaluated when you enter it. Currently we were building up the
llvm-hs-pure AST inside our REPL, and then converting it to an actual
LLVM IR module in main when we called buildModuleT.

In order to do this line-by-line JITing, we'll need the actual LLVM
module when we enter the line. This will prepare us for the craziness
that will come in the following commits