A free-form `attrsOf str` option that is merged with the /etc/os-release
builder, allowing downstreams to customise arbitrary os-release fields.
This is separate from the variant option, as using an attribute set
merge means one gets an infinte recursion when making extraOSReleaseArgs
a recursive set, and the variant attribute is useful to define elsewhere
or multiple times.
Ditto for /etc/lsb-release.
Signed-off-by: Fernando Rodrigues <alpha@sigmasquadron.net>
02e1f93cb4