WIP: Preserve gitignore files when cleaning native builds
This is in order to partially solve the problem of the build system changing files that are revision-tracked by git, while minimising the number of components that we have to touch to achieve this.
So far, I've only tacked CModule. It's a little clunky though, so I thought I'd submit it for review before doing the others in case anyone has a better idea of how to achive the same effect.
Note that to see the desired effect, you need the new version of amu that will be included in the next DDE release. So most people will have to be patient before trying it!