build: enable libarchive by default

Or libcve, as the vlc developers call it.

wscript

@@ -421,7 +421,6 @@ iconv support use --disable-iconv.",
         'name': '--libarchive',
         'desc': 'libarchive wrapper for reading zip files and more',
         'func': check_pkg_config('libarchive >= 3.0.0'),
-        'default': 'disable',
     }
 ]