F4PGA is barely maintained

[mcgoron-peter]

F4PGA is the synthesis toolchain that LiteX (the build system) relies upon.

1. F4PGA relies on plugins for other software (yosys, vpr, etc.) and those are on very outdated versions. For example, yosys is currently on version 0.37, but F4PGA uses version 0.19.
2. F4PGA pulls architecture definitions that are years out of date at this point, and nobody has put in the effort to test the new definitions.

The build system seems to work fine and will probably continue to work fine for the duration of development, but we should look out for alternative toolchains that have better support. LiteX supports

1. yosys+nextpnr
2. https://github.com/openXC7 , a fairly new project run by one guy

[mcgoron-peter]

YosysHQ/yosys#3670
Here's a fix for a block ram problem that is not in current F4PGA