This commit is based on mu-impl-ref2@e4b223c.
This commit is tagged before changing the API using the symbolic IR builder (issue64-symbolic-irbuilder branch).
The code up to this commit still has some weird bugs.
Compiling the SOM interpreter using both text and api backend and compare the execution trace is what I was up to.
This is the branch point if I ever come back to solving this bug.

Able to compile a minimal PyPy interpreter (with --no-allworkingmodules option).

MuAPI RPython binding v1.0