more work on install scripts

mullvad-vpn-daemon/mullvad-vpn-daemon.post-install

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -eu
+
+echo "mullvad post-install"
+
+# Overwrite the cached relay list with the one embedded in the package.
+mkdir -p /var/cache/mullvad-vpn \
+  && cp /usr/share/mullvad-vpn/relays.json /var/cache/mullvad-vpn/relays.json \
+  || echo "failed to install /var/cache/mullvad-vpn/relays.json"