Debian based distributions need writable-var in tar.profile

[glitsj16]

On Ubuntu 16.04, dpkg/synaptic throws the below errors when sandboxing tar and installing/upgrading a package:

/bin/tar: ./prerm: Cannot open: Read-only file system
/bin/tar: ./md5sums: Cannot open: Read-only file system
/bin/tar: ./control: Cannot open: Read-only file system
/bin/tar: ./postinst: Cannot open: Read-only file system
/bin/tar: ./postrm: Cannot open: Read-only file system
/bin/tar: ./triggers: Cannot open: Read-only file system
/bin/tar: ./preinst: Cannot open: Read-only file system
/bin/tar: .: Cannot utime: Read-only file system
/bin/tar: .: Cannot change ownership to uid 0, gid 0: Read-only file system
/bin/tar: Exiting with failure status due to previous errors
dpkg: error processing archive /var/cache/apt/archives/php7.1-xml_7.1.23-2+ubuntu16.04.1+deb.sury.org+1_amd64.deb (--unpack):
failed to open package info file '/var/lib/dpkg/tmp.ci/control' for reading: No such file or directory
Errors were encountered while processing:
/var/cache/apt/archives/php7.1-xml_7.1.23-2+ubuntu16.04.1+deb.sury.org+1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover

This can be fixed by adding writable-var to the tar profile.

Regards.