xcelium makefile does nothing

[Jbalkind]

I'm running into an issue trying to use the xcelium backend. When running with --setup --build (i.e. not looking to actually run the simulation), the produced makefile doesn't actually do anything. It just gives some message about not having anything to do.

For my use case, I don't actually use the final run from fusesoc and instead call xrun independently inside our regression testing infrastructure. For my case, I was able to make a change to add an elaborate make target and have that be the default, but clearly that doesn't work for everyone's purposes. See my patch here: https://github.com/Jbalkind/edalize/commit/90cbdc5f246f457e217ec6f8f47bf9436146250f

I'm wondering what the correct approach is for this kind of thing. I looked in a couple of backends but only saw run_main() and so wasn't sure how --build was meant to be handled in general. It'd be nice to fix up the backends to be a bit more consistent about this.