Remove libselinux.so.1 dependency of the AppImage

[Dirk Hohndel]

On Sun, Feb 26, 2017 at 05:15:03PM +0100, probono wrote:
> Dear Subsurface developers,
> 
> the binaries inside the Subsurface AppImage require libselinux.so.1
> which typically is not available on Arch Linux (e.g., Antergos) in the
> default installation. Hence it would be good if it could be disabled
> during compilation, or a mock (dummy) .so could be bundled inside the
> AppImage, satisfying the dependency.
> 
> https://github.com/probonopd/AppImages/issues/83#issuecomment-282566072

I have tried to figure out how to do that and failed. I don't know why the
CentOS build creates that libselinux.so dependency and my attempts to fix
the issue failed. I think that bundling a fake lib could cause other
problems, but I'm not sure about that one.

Suggestions (ideally in the form of patches) would be welcome!

/D