Resurrect nogui executable

[vladfi1]

Also allows building headless, which is useful for bots.

[ryanmcgrath]

macOS still uses this, just fyi - so maybe instead of commenting it out just block it off with an #ifdef __APPLE_.

[vladfi1]

Issue is that the nogui build will still fail since we don't compile DolphinWX at all in nogui.

[vladfi1]

I think I have an idea for a fix...

[ryanmcgrath]

Well, sure - #ifndef NOGUI or whatever on the imports and raise/lower calls would suffice, no?

[vladfi1]

So I need to fix the dependencies on DolphinWX which are currently just commented out (and are likely resulting in all the build failure).

1. SlippiTimer.cpp: maybe I can just move it into DolphinWX? Need to check where it is actually used.
2. main_frame->Raise/LowerRenderWindow: The issue is that DolphinWX won't exist in the nogui build. Cleanest thing to do here might be to set define NOGUI and then block those parts off with an #ifndef NOGUI.

[vladfi1]

2. main_frame->Raise/LowerRenderWindow: The issue is that DolphinWX won't exist in the nogui build. Cleanest thing to do here might be to set define NOGUI and then block those parts off with an #ifndef NOGUI.

Actually this won't work because SlippiLib is built independently of gui/nogui. As a workaround I've added a fix for this with some stub functions in UICommon.h that are implemented in either DolphinWX or DophinNoGui.