utils: codegen: Make users depend on controls.py in meson

Currently, modifying `controls.py` does not make those build targets dirty
that use a script that includes it (e.g. `gen-controls.py`) because meson
has no knowledge of this dependency. Add `depend_files` to each
`custom_target()` invocation to fix this.

Ideally it would be possible to attach this dependency to `gen_controls`,
`gen_gst_controls`, etc. objects themselves, so that repetition is
avoided, but this does not seem possible at the moment.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Acked-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

src/gstreamer/meson.build

@@ -33,6 +33,7 @@ libcamera_gst_sources += custom_target('gstlibcamera-controls.cpp',
                                        output : 'gstlibcamera-controls.cpp',
                                        command : [gen_gst_controls, '-o', '@OUTPUT@',
                                                   '-t', gen_gst_controls_template, '@INPUT@'],
+                                       depend_files : [py_mod_controls],
                                        env : py_build_env)
 
 libcamera_gst_cpp_args = [