Specify required Glibc version in AppImage

Honestly I wasn’t even aware that packaging Glibc was possible, this looks like an amazing tool for max compatibility in exchange for a larger file size. Out of curiosity though, is adding something like this a feature you’d be interested in? I’d be happy to whip up an alternative AppRun that looks for a dialog implementation (zenity, kdialog, etc) on the host system in case an error occurs