finalize.d: Ensure var/tmp in container root

There's a crazy history around this; what we really want is
to have this reliably generated by tmpfiles.d, the handling
for which I want to move to bootc. For now let's wedge this
into finalize.d alongside the few others here.

Signed-off-by: Colin Walters <walters@verbum.org>

minimal/finalize.d/01-var.sh

@@ -4,3 +4,4 @@ set -xeuo pipefail
 ln -s ../run var/run
 # https://gitlab.com/fedora/bootc/tracker/-/issues/58
 mkdir -p var/lib/rpm-state
+test -d var/tmp || mkdir -m 1777 var/tmp