`sample_pdk` and Xyce not playing nice

[dan-fritchman]

On some level related to https://github.com/Vlsir/Vlsir/issues/47.

It's not clear how far the current Xyce issues go, but on at least two machines, they include failing to comprehend the Hdl21 sample_pdk. Xyce seems to treat its devices as... nothing? It's as though they're not in the netlist.