[fusesoc] Compile DPI modules into shared libraries and link them afterwards

[imphil]

Currently we compile all DPI code together with the Verilator-generated C++ code. We need to extend fusesoc to first compile the DPI modules into shared libraries, and then pass those libraries to the Verilator makefile to link all components together into one simulation.

This allows us to actually compile C code with a C compiler, as opposed to a C++ compiler (that's what we do right now).

[aytong]

Philipp, who should this be assigned to, and what's the best "Type" for this issue: Tooling, SW, or DV?

[aytong]

Scrubbing stale issues. @imphil , what's the current status on this? Thanks.

[imphil]

still valid

[GregAC]

We haven't seen any issues with compiling our DPI C code with a C++ compiler so closing this.