Add Valgrind to CI

* Also pass `$*` to `configure` when invoking `ci-build.sh`, so one can
  e.g. run `./ci-build.sh --without-xscreensaver`

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Dockerfile.ubuntu

@@ -28,6 +28,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   pkg-config \
   python3-dev \
   python-dev-is-python3 \
+  valgrind \
   libsqlite3-dev \
   libgdk-pixbuf-2.0-dev \
   libqrencode-dev