This makes the emulator suitable to run the base SMS recipe.

It seems to be picky about where it accepts its link flags.

VDP kinda works. Can see the Collapse OS prompt with SMS base recipe
if `STDIO_GETC` gets replaced with infinite loop (no input emul yet).

I implement the screen using XCB which is much more friendly
than z80e's SDL+CMake for development machines that want to install
minimal dependencies (for example, a port-less OpenBSD rig).