[Buildroot] [git commit branch/2022.02.x] package/opencv4: BR2_PACKAGE_OPENCV4_LIB_DNN requires protobuf

[Peter Korsgaard]

commit: https://git.buildroot.net/buildroot/commit/?id=7bce3d6a97393772b4ed9da35fd3991977b7ec19
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2022.02.x

Opencv4 requires protobuf library otherwise it disables DNN:
```
if(NOT HAVE_PROTOBUF)
  ocv_module_disable(opencv_dnn)
endif()
```
https://github.com/opencv/opencv/blob/4.x/modules/dnn/CMakeLists.txt#L5-L7
So let's "select BR2_PACKAGE_OPENCV4_WITH_PROTOBUF" if
BR2_PACKAGE_OPENCV4_LIB_DNN is enabled.

Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
(cherry picked from commit b0d3c25cc8017e92dbdedf1a1dde6f4dc4408332)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 package/opencv4/Config.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/package/opencv4/Config.in b/package/opencv4/Config.in
index d7a391a40a..5b07f52ba1 100644
--- a/package/opencv4/Config.in
+++ b/package/opencv4/Config.in
@@ -34,11 +34,14 @@ config BR2_PACKAGE_OPENCV4_LIB_DNN
 	bool "dnn"
 	# dnn needs fenv.h which is not provided by uclibc
 	depends on !BR2_TOOLCHAIN_USES_UCLIBC
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
+	select BR2_PACKAGE_OPENCV4_WITH_PROTOBUF
 	help
 	  Include opencv_dnn (Deep Neural Networks) module into the
 	  OpenCV build.
 
 comment "dnn needs a glibc or musl toolchain"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_USES_UCLIBC
 
 config BR2_PACKAGE_OPENCV4_LIB_FEATURES2D