[Buildroot] [git commit branch/2022.02.x] package/opencv4: BR2_PACKAGE_OPENCV4_LIB_OBJDETECT requires BR2_PACKAGE_OPENCV4_LIB_DNN

[Peter Korsgaard]

commit: https://git.buildroot.net/buildroot/commit/?id=3fa2a869740e365b1800146106f1e6f3d5e902a9
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2022.02.x

Opencv4 library objdetect needs library dnn, otherwise it throws:
```
-- Module opencv_objdetect disabled because opencv_dnn dependency can't be resolved!
```
So let's "select BR2_PACKAGE_OPENCV4_LIB_DNN" if
BR2_PACKAGE_OPENCV4_LIB_OBJDETECT 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 e229943785534e0884c62c7346a8c6df8d565e1e)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 package/opencv4/Config.in | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/package/opencv4/Config.in b/package/opencv4/Config.in
index 5b07f52ba1..88a7a01151 100644
--- a/package/opencv4/Config.in
+++ b/package/opencv4/Config.in
@@ -153,14 +153,21 @@ config BR2_PACKAGE_OPENCV4_LIB_ML
 
 config BR2_PACKAGE_OPENCV4_LIB_OBJDETECT
 	bool "objdetect"
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC # dnn support
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS # dnn support
 	# opencv_core dependency is already enabled
 	select BR2_PACKAGE_OPENCV4_LIB_CALIB3D
+	select BR2_PACKAGE_OPENCV4_LIB_DNN
 	select BR2_PACKAGE_OPENCV4_LIB_IMGPROC
 	select BR2_PACKAGE_OPENCV4_LIB_ML
 	help
 	  Include opencv_objdetect (object detection) module into the
 	  OpenCV build.
 
+comment "objdetect needs a glibc or musl toolchain"
+	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
+	depends on BR2_TOOLCHAIN_USES_UCLIBC
+
 config BR2_PACKAGE_OPENCV4_LIB_PHOTO
 	bool "photo"
 	select BR2_PACKAGE_OPENCV4_LIB_IMGPROC