Allow running all the tests with the daemon

When `NIX_DAEMON_PACKAGE` is set, make all the tests use the Nix daemon.
That way we can test every piece of Nix functionality both with and
without the daemon.

Tests for which using the daemon isn’t possible or doesn’t make sens can
selectively be disabled with `needLocalStore`

tests/post-hook.sh

@@ -5,6 +5,9 @@ clearStore
 rm -f $TEST_ROOT/result
 
 export REMOTE_STORE=file:$TEST_ROOT/remote_store
+echo 'require-sigs = false' >> $NIX_CONF_DIR/nix.conf
+
+restartDaemon
 
 # Build the dependencies and push them to the remote store
 nix-build -o $TEST_ROOT/result dependencies.nix --post-build-hook $PWD/push-to-store.sh