Makefile gtkwave sim and xserver recipes for WSL FPGA programming

Makefile

PROJ = ulx3s_adda
sim: 
	rm -f $(PROJ).vcd
	iverilog  -o $(PROJ).vvp $(PROJ).v $(PROJ)_tb.v
	vvp $(PROJ).vvp
	export DISPLAY=:0

## if we are running in WSL, we need a bit of help for GUI XWindows
## and sometimes the WSL username is not the same as the Windows username & we need the *windows* user path.
## this is the Windows %USER% environment variable when called from makefile: $(shell cmd.exe /c "echo $$USER")
	@if [ "$(shell grep Microsoft /proc/version)" != "" ]; then   \
			cp /mnt/c/cygwin64/home/$(shell cmd.exe /c "echo $$USER")/.Xauthority   ~/.Xauthority; \
	fi

	(gtkwave $(PROJ).vcd $(PROJ)_savefile.gtkw)&

xserver:
## launch the Windows cygwin64 startxwin when WSL is detected
	@if [ "$(shell grep Microsoft /proc/version)" != "" ]; then   \
		echo "Launching Windows XServer from WSL...";         \
		(/mnt/c/cygwin64/bin/run.exe --quote /usr/bin/bash.exe -l -c " exec /usr/bin/startxwin -- -listen tcp -nowgl")&  \
	else                                                          \
		echo "Not launching WSL XServer!" ;                   \
	fi