Use $(EDALIZE_LAUNCHER) envvar when calling xtclsh

[hipolitoguzman]

The $(EDALIZE_LAUNCHER) environment variable was missing from the calls to xtclsh in the code that generates the Makefile(s), so ISE docker images could not be used (the custom launcher was silently ignored)

The calls to impact seem to be a different beast since they are managed by the _run_tool() function, which (from the tests I have made locally) also doesn't seem to read the $(EDALIZE_LAUNCHER) variable. I suppose this would also happen with the other EDA tools that are invoked by the same function (such as radiantc, quartus_pgm, sby or vsim), but I'm not familiarized enough with the codebase to really look into it.