Silence verbose output when VERBOSE environment variable is not set

[yqxk]

Hello,

I sometimes run appimages in docker containers, which do not allow mounting of filesystems by default, so I run them with

APPIMAGE_EXTRACT_AND_RUN=1 NO_CLEANUP=1 <path to appimage>

After the first execution, subsequent runs produce many lines of "File exists and file size matches, skipping". It would be nice if we could silence these informational messages (redirecting stderrto /dev/null is not ideal as this also redirects error messages from the bundled app).

This string is output here, and the function this lives in already has access to a verbosity flag here; so it looks reasonably straightforward to implement it. Would this be possible?

Thanks for your work on this!

[TheAssassin]

PRs welcome refactoring the logging.