package/opencv3: add patch to fix CMake 4 build issue

Add a small patch to fix CMake 4 build issues. Unfortunately, while
cmake/OpenCVMinDepVersions.cmake provides a MIN_VER_CMAKE that we
could pass on the command line, cmake/OpenCVGenPkgconfig.cmake doesn't
use it, so we anyway have to patch the package.

Since opencv3 is basically unmaintained, there is no point sending
this patch upstream.

Fixes:

  https://autobuild.buildroot.net/results/cc857993920607958dd817c6a877ed9386c05738/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/opencv3/0001-cmake-set-minimum-required-CMake-version-to-3.5.patch

@@ -0,0 +1,41 @@
+From 3b7311f48ef70127ddad7c7ea9c008fa6af3a9a1 Mon Sep 17 00:00:00 2001
+From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+Date: Thu, 25 Dec 2025 23:11:27 +0100
+Subject: [PATCH] cmake: set minimum required CMake version to 3.5
+
+This fixes build with CMake 4.
+
+Upstream: N/A, opencv 3.x is no longer maintained
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+---
+ cmake/OpenCVGenPkgconfig.cmake   | 2 +-
+ cmake/OpenCVMinDepVersions.cmake | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/cmake/OpenCVGenPkgconfig.cmake b/cmake/OpenCVGenPkgconfig.cmake
+index 425c0faa3b..9642a4b983 100644
+--- a/cmake/OpenCVGenPkgconfig.cmake
++++ b/cmake/OpenCVGenPkgconfig.cmake
+@@ -110,7 +110,7 @@ endif()
+ # =============================================================================
+ else() # DEFINED CMAKE_HELPER_SCRIPT
+ 
+-cmake_minimum_required(VERSION 2.8.12.2)
++cmake_minimum_required(VERSION 3.5)
+ cmake_policy(SET CMP0012 NEW)
+ include("${CMAKE_HELPER_SCRIPT}")
+ include("${OpenCV_SOURCE_DIR}/cmake/OpenCVUtils.cmake")
+diff --git a/cmake/OpenCVMinDepVersions.cmake b/cmake/OpenCVMinDepVersions.cmake
+index e67856bb97..eb7a6d861e 100644
+--- a/cmake/OpenCVMinDepVersions.cmake
++++ b/cmake/OpenCVMinDepVersions.cmake
+@@ -1,5 +1,5 @@
+ if(NOT DEFINED MIN_VER_CMAKE)
+-  set(MIN_VER_CMAKE 2.8.12.2)
++  set(MIN_VER_CMAKE 3.5)
+ endif()
+ set(MIN_VER_CUDA 6.5)
+ set(MIN_VER_PYTHON2 2.7)
+-- 
+2.52.0
+