Some people's workflows involve not using `pip`. This is not
a recommended way to use nMigen, but is prevalent enough for good
enough reason that we try to keep them working anyway.
Do not use yosys binaries with unparseable version numbers. This ensures
that nmigen always knows what version of yosys it is generating RTLIL
for.
The effect of this change is that if the version number of the system
yosys is unparsable, nmigen will attempt to fallback to the builtin
Yosys.
Fixes#409.
The nmigen-yosys PyPI package provides a custom, minimal build of
Yosys that uses (at the moment) wasmtime-py to deliver a single
WASM binary that can run on many platforms, and eliminates the need
to build Yosys from source.
Not only does this lower barrier to entry for new nMigen developers,
but also decouples nMigen from Yosys' yearly release cycle, which
lets us use new features and drop workarounds for Yosys bugs earlier.
The source for the nmigen-yosys package is provided at:
https://github.com/nmigen/nmigen-yosys
The package is built from upstream source and released automatically
with no manual steps.
Fixes#371.
