Doesn't build on NetBSD due to its use of deprecated statfs.

There is a known security issue with [wip/xar]:

 http://code.google.com/p/xar/source/detail?r=225
 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-0055
 http://secunia.com/advisories/39774/
 https://nvd.nist.gov/vuln/detail/CVE-2017-11124
 https://nvd.nist.gov/vuln/detail/CVE-2017-11125
 https://nvd.nist.gov/vuln/detail/CVE-2018-17093
 https://nvd.nist.gov/vuln/detail/CVE-2018-17094