package/opencv-contrib: propagate opencv4 dependencies

Commit a7736afacaef (package/opencv4-contrib: properly note dependencies
between modules) forgot to propagate the dependencies of selected
symbols, causing unmet dependencies warnings (unfortunately, not
errors), such as:

    $ KCONFIG_SEED=0x9F66F854 make randconfig
    WARNING: unmet direct dependencies detected for BR2_PACKAGE_OPENCV4_LIB_DNN
      Depends on [n]: BR2_PACKAGE_OPENCV4 [=y] && !BR2_TOOLCHAIN_USES_UCLIBC [=y] && BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS [=y]
      Selected by [y]:
      - BR2_PACKAGE_OPENCV4_CONTRIB_LIB_DNN_OBJDETECT [=y] && BR2_PACKAGE_OPENCV4_CONTRIB [=y]

Propagate the dependencies and add associated comments.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Woodrow Douglass <wdouglass@carnegierobotics.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit a2e01b23fc441a4be4416e68d91e331e00db3bbd)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/opencv4-contrib/Config.in

@@ -74,19 +74,31 @@ config BR2_PACKAGE_OPENCV4_CONTRIB_LIB_DATASETS
 
 config BR2_PACKAGE_OPENCV4_CONTRIB_LIB_DNN_OBJDETECT
 	bool "dnn_objdetect"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS # opencv4 dnn
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC # opencv4 dnn
 	select BR2_PACKAGE_OPENCV4_LIB_DNN
 	help
 	  Object Detection using CNNs -- Implements compact CNN Model
 	  for object detection. Trained using Caffe but uses
 	  opencv_dnn module.
 
+comment "dnn_objdetect needs a glibc or musl toolchain"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC
+
 config BR2_PACKAGE_OPENCV4_CONTRIB_LIB_DNN_SUPERRES
 	bool "dnn_superres"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS # opencv4 dnn
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC # opencv4 dnn
 	select BR2_PACKAGE_OPENCV4_LIB_DNN
 	help
 	  Superresolution using CNNs -- Contains four trained
 	  convolutional neural networks to upscale images.
 
+comment "dnn_superres needs a glibc or musl toolchain"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC
+
 config BR2_PACKAGE_OPENCV4_CONTRIB_LIB_DNNS_EASILY_FOOLED
 	bool "dnns_easily_fooled"
 	help