tests: implement test for nix log with ssh-ng:// builds

A few notes:

* The `echo hi` is needed to make sure that a file that can be read by
  `nix log` is properly created (i.e. some output is needed). This is
  known and to be fixed in #6051.
* We explicitly ignore the floating-CA case here: the `$out` of `input3`
  depends on `$out` of `input2`. This means that there are actually two
  derivations - I assume that this is because at eval time (i.e.
  `nix-instantiate -A`) the hash of `input2` isn't known yet and the
  other .drv is created as soon as `input2` was built. This is another
  issue on its own, so we ignore the case here explicitly.

tests/build-remote.sh

@@ -54,6 +54,14 @@ nix path-info --store $TEST_ROOT/machine3 --all \
   | grep -v builder-build-remote-input-2.sh \
   | grep builder-build-remote-input-3.sh
 
+
+if [[ -z "$CONTENT_ADDRESSED" ]]; then
+  for i in input1 input3; do
+    drv="$(nix-instantiate $file -A passthru.$i --store $TEST_ROOT/machine0 --arg busybox $busybox)"
+    nix log --store $TEST_ROOT/machine0 "$drv"
+  done
+fi
+
 # Behavior of keep-failed
 out="$(nix-build 2>&1 failing.nix \
   --builders "$(join_by '; ' "${builders[@]}")"  \