This is not needed but it does not cost much to do it for all
potentially supported format in libarchive. XZ and LZMA are not
builtin libarchive and require external lib but if
CMAKE_USE_SYSTEM_LIBARCHIVE is ON then we may get it for free.
This will be needed to use cmArchiveWrire in cmCPackArchiveGenerator
with the same feature set as before. Note that adding zip
support to libarchive-wrapper would also makes it easy to add
a new -E zip command to cmake commands.
Eric NOULARD
Brad King