Problem and How to reproduce

If you run cocotb with verilator as a simulation backend an error pops up on Ubuntu 22.04 LTS.

First source the enviroment. Otherwise you will see this error "ModuleNotFoundError: No module named 'encodings'".
- source <install-path>/oss-cad-suite/enviroment
Then run any cocotb example with verilator. Error:
```
File "/mnt/second/applications/lin/oss-cad-suite/lib/python3.8/site-packages/cocotb-1.8.0.dev0-py3.8-linux-x86_64.egg/cocotb/handle.py", line 32, in <module>
import ctypes
File "/mnt/second/applications/lin/oss-cad-suite/lib/python3.8/ctypes/__init__.py", line 7, in <module>
from _ctypes import Union, Structure, Array
ImportError: libffi.so.7: cannot open shared object file: No such file or directory
```
Explanation

Cocotb is trying to import ctypes which is a standard python library. But unfortunately it depends on another system library called libffi7.

Solution

The library is removed in Ubuntu 22.04. So, the solution is to install libffi7 back.
```
sudo apt install libffi7
```
Comments

I am not sure if this is an oss-cad-suite bug. But, it would be nice if that libffi library can be added as a dependency. Also, since this has happened due to my distro I will close the issue.

YosysHQ / oss-cad-suite-build