[trivial] Ignore split-debug.sh #8197

This is being generated since #8188, should it be in .gitignore?

Hmmm. Haven't run this but, going off my recollection of Gitian builds (haven't done one in awhile), all the stuff built in a Gitian container is self-contained and built away from the normal directory structure. So, I don't think this patch is necessary. Nice thought, though, and I could be totally wrong. :)

@droark .gitignore has nothing to do with gitian, and is never "necessary"; it's purely for programmer convenience.

@droark You would be right if split-debug.sh was only generated by the gitian descriptors. However the build system itself generates the file, so it does have to be ignored, as that's how we define the contents of .gitignore in this project.

(@sipa is right and it is not "necessary" to do so, however it prevents this generated file from accidentally being checked in)

@laanwj @sipa - Thanks for the correction. What I meant with my original comment was that I was under the impression that the generated file wouldn't be picked up in the original directory, and that .gitignore didn't have to be updated. (Obviously, .gitignore and Gitian are unrelated. I didn't mean to imply that.) I was wrong, though. C'est la vie. :)