AST Compare tests libpypa vs cpython

@kmod 
I have implemented a priliminary patch for the suggested check.
It already shows some issues. I will check them out and fix them.
Heh ok, though for the sake of curiosity, could you try putting `$(error $(LLVM_LDFLAGS))` somewhere in the Makefile and posting what it outputs?  I'm pretty sure we don't use tinfo in Pyston so the dependency has to be coming from LLVM, and is supposed to be covered by the `llvm-config --ldflags` invocation.