meson: add script to print the options before configuring a builddir

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>

docs/meson.html

@@ -58,7 +58,9 @@ and your local settings.
 <p>
 Meson does not currently support listing options before configure a build
 directory, but this feature is being discussed upstream.
-For now, the only way to see what options exist is to look at the
+For now, we have a <code>bin/meson-options.py</code> script that prints
+the options for you.
+If that script doesn't work for some reason, you can always look in the
 <code>meson_options.txt</code> file at the root of the project.
 </p>