libcamera: Make pipeline handlers selectable at compile time

Add a 'pipelines' project option that specifies which pipeline handlers
to compile in. The corresponding IPA modules are automatically selected.
The default is to compile all pipeline handlers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/pipeline/meson.build

@@ -1,4 +1,3 @@
-subdir('ipu3')
-subdir('rkisp1')
-subdir('uvcvideo')
-subdir('vimc')
+foreach pipeline : get_option('pipelines')
+    subdir(pipeline)
+endforeach