Compressed archives now contain a single root which consists of the file or
folder being compressed. Before, the archive root contained the full relative
path form the current working directory to the compressed file or folder. This
is unintuitive in most cases and not dwim.
The log level can now be set by environment variable `XWIM_LOGLEVEL`.
Alternatively a default log level per build type (determined by NDEBUG flag) is
used.
