Examples Makefiles define PARTNAME := xc7a35tcsg324-1 => toolchain builds

I created a Migen design from scratch and migen.build.platforms.arty_ay7.Platform uses 'device="xc7a35ticsg324-1L"' as does litex.boards.platforms.arty.Platform

The migen/litex generates a buildscript that is close to but different than the one in the examples and it doesn't work ... the obvious things were 'synth' instead 'symbiflow_synth', 'place' instead of ... and similar but different argument signatures

Fixing the obvious still failed ... had also change the device to the -1 .. the -1L was failing in Yosys at step 8 ... .JSON generation