Fix OpenCVConfig.cmake generated for Android platform (issue #2496)

* fix path to libraries in Android SDK
* allow to link to opencv_java.so as Android.mk does

To link to opencv_java.so you can either change your cmake to find OpenCV as

    find_package(OpenCV opencv_java)

or pass -DOpenCV_FIND_COMPONENTS=opencv_java to your cmake command

cmake/OpenCVGenConfig.cmake

@@ -53,6 +53,10 @@ if(OpenCV_LIB_COMPONENTS)
   list(REMOVE_ITEM OPENCV_MODULES_CONFIGCMAKE ${OpenCV_LIB_COMPONENTS})
 endif()
 
+if(BUILD_FAT_JAVA_LIB AND HAVE_opencv_java)
+  list(APPEND OPENCV_MODULES_CONFIGCMAKE opencv_java)
+endif()
+
 macro(ocv_generate_dependencies_map_configcmake suffix configuration)
   set(OPENCV_DEPENDENCIES_MAP_${suffix} "")
   set(OPENCV_PROCESSED_LIBS "")
@@ -126,8 +130,13 @@ configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/OpenCVConfig-version.cmake.
 set(OpenCV_INCLUDE_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/${OPENCV_INCLUDE_INSTALL_PATH}/opencv" "\${OpenCV_INSTALL_PATH}/${OPENCV_INCLUDE_INSTALL_PATH}\"")
 
 set(OpenCV2_INCLUDE_DIRS_CONFIGCMAKE "\"\"")
-set(OpenCV_LIB_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/${OPENCV_LIB_INSTALL_PATH}\"")
-set(OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/${OPENCV_3P_LIB_INSTALL_PATH}\"")
+if(ANDROID)
+  set(OpenCV_LIB_DIRS_CONFIGCMAKE          "\"\${OpenCV_INSTALL_PATH}/sdk/native/libs/\${ANDROID_NDK_ABI_NAME}\"")
+  set(OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/sdk/native/3rdparty/libs/\${ANDROID_NDK_ABI_NAME}\"")
+else()
+  set(OpenCV_LIB_DIRS_CONFIGCMAKE          "\"\${OpenCV_INSTALL_PATH}/${OPENCV_LIB_INSTALL_PATH}\"")
+  set(OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/${OPENCV_3P_LIB_INSTALL_PATH}\"")
+endif()
 if(INSTALL_TO_MANGLED_PATHS)
   string(REPLACE "OpenCV" "OpenCV-${OPENCV_VERSION}" OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE "${OPENCV_3P_LIB_INSTALL_PATH}")
   set(OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE "\"\${OpenCV_INSTALL_PATH}/${OpenCV_3RDPARTY_LIB_DIRS_CONFIGCMAKE}\"")

cmake/templates/OpenCVConfig.cmake.in

@@ -151,6 +151,7 @@ endif()
 # ==============================================================
 if(NOT OpenCV_FIND_COMPONENTS)
   set(OpenCV_FIND_COMPONENTS ${OpenCV_LIB_COMPONENTS})
+  list(REMOVE_ITEM OpenCV_FIND_COMPONENTS opencv_java)
   if(GTest_FOUND OR GTEST_FOUND)
     list(REMOVE_ITEM OpenCV_FIND_COMPONENTS opencv_ts)
   endif()