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>

include/libcamera/meson.build

@@ -90,6 +90,7 @@ foreach mode, entry : controls_map
                                      command : [gen_controls, '-o', '@OUTPUT@',
                                                 '--mode', mode, '-t', template_file,
                                                 '-r', ranges_file, '@INPUT@'],
+                                     depend_files : [py_mod_controls],
                                      env : py_build_env,
                                      install : true,
                                      install_dir : libcamera_headers_install_dir)