Dockerfile restructure + Lakeroad Yosys plugin

[gussmith23]

This PR does two things that are only slightly related (sorry about that):

• Introduces Lakeroad Yosys plugin, plus tests and documentation
• Restructures/simplifies/solidifies the Dockerfile

The Lakeroad Yosys plugin is a plugin for the Yosys synthesis tool which calls Lakeroad to compile Verilog modules. During the process of adding the plugin into CI, I realized we needed to build Yosys from source, which led me to restructuring the Dockerfile.

The restructure of the Dockerfile does a few things:

• Moves dependencies into an explicit file (rather than adhoc or git submodules)
• Pulls specific binaries out of oss-cad-suite and deletes the unneeded ones

[gussmith23]

Just to log: there's a weird libc++ issue happening on the GitHub Actions runners that I can't reproduce locally. When I try to load the lakeroad.so for the plugin, it's complaining that it can't find an updated libcxx 3.4.29. I tried building w/o boost, but it doesn't seem to be coming from boost. I wonder if it's a Yosys thing?

[gussmith23]

Okay, so it seems like the issue is coming from the prebuilt Yosys.

Here's the actual error:

ERROR: Can't load module `/root/lakeroad/yosys-plugin/lakeroad.so': /root/oss-cad-suite/lib/libstdc++.so.6: version `GLIBCXX_3.4.29' not found (required by /root/lakeroad/yosys-plugin/lakeroad.so)

When I build yosys from source, I no longer get the error.

[gussmith23]

See YosysHQ/oss-cad-suite-build#91.