Single-module offload compilation

[penzn]

https://github.com/penzn/omp-wasi-parallel/tree/master/openmp-offload

This is obviously a POC as there is no bridge between OpenMP offload runtime and wasi-parallel, and for the time being it is imported. With a relatively simple change to compiler frontend (linked in the repo) we can support full-program compilation into a single file.

Since offload API doesn't share data with the host directly runtime can pick up device compilation from the module without additional analysis.