Suggestion: make Tube support optional for the BBC Micro

[cmdrj]

The 6502 second processor via the Tube interface was used by very little software on the BBC Micro.

Clock Signal (v26.02.20) will currently not start without the v1.10 Tube ROM, which is nigh impossible to find. There are files out there purporting to be the Tube ROM, but Clock Signal rejects them.

Obviously we can’t expect Clock Signal to distribute this ROM, but as a second processor is definitely not required to play Citadel 2, I think making it optional rather than required would be good.

[TomHarte]

I think the emulator is misdiagnosing that specific disk image, and believes it will use a second processor. I'll have to look at its means of diagnosis more closely.

[cmdrj]

FWIW, it did the same on the Super Space Invaders image from the same source, and that’s an ancient Acornsoft game that doesn’t push the computer at all.

[cmdrj]

It must be something in my build process. I’ve just tried the prebuilt binary and it works fine.