update yosys to 0.18
There are numerous new features from 0.13 to 0.18, including improved support for more backends, SystemVerilog and Verific.
For a complete list of changes, please see https://github.com/YosysHQ/yosys/releases
- passed all cases in the check step;
- install, run example in examples/osu035 with make, see result file example.edif.
- run example in examples/python-api, check if it produces a plot.
Reviewers: Triage Team, Staudey
Reviewed By: Staudey
Differential Revision: https://dev.getsol.us/D13336