Fixed some cmake 2.6 compatibility issues.

CMakeLists.txt

@@ -37,14 +37,14 @@ endif(NOT CMAKE_TOOLCHAIN_FILE)
 # Top level OpenCV project
 # --------------------------------------------------------------
 if(NOT IOS)
-	cmake_minimum_required(VERSION 2.6)
+	cmake_minimum_required(VERSION 2.6.3)
 else()
 	cmake_minimum_required(VERSION 2.8)
 endif()
 project(OpenCV)
 
 set(CMAKE_CONFIGURATION_TYPES "Debug;Release" CACHE STRING "Configs" FORCE)
-if(DEFINED CMAKE_BUILD_TYPE)
+if(DEFINED CMAKE_BUILD_TYPE AND CMAKE_VERSION VERSION_GREATER "2.8")
     set_property( CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS ${CMAKE_CONFIGURATION_TYPES} )
 endif()
 
@@ -448,7 +448,12 @@ endif()
 set(WITH_TBB OFF CACHE BOOL "Include Intel TBB support")
 set(WITH_IPP OFF CACHE BOOL "Include Intel IPP support")
 set(WITH_EIGEN ON CACHE BOOL "Include Eigen2/Eigen3 support")
-set(WITH_CUDA ON CACHE BOOL "Include NVidia Cuda Runtime support")
+
+if( CMAKE_VERSION VERSION_GREATER "2.8")
+    set(WITH_CUDA ON CACHE BOOL "Include NVidia Cuda Runtime support")
+else()
+    set(WITH_CUDA OFF CACHE BOOL "Include NVidia Cuda Runtime support")
+endif()
 
 set(WITH_OPENNI OFF CACHE BOOL "Include OpenNI support")
 set(WITH_XIMEA OFF CACHE BOOL "Include XIMEA cameras support")
@@ -824,7 +829,7 @@ if (BUILD_JAVA_SUPPORT)
             endif()
 
             SET(ANDROID_SDK_TARGET ${ANDROID_SDK_TARGET} CACHE STRING "SDK target for Android tests and samples")
-            if (ANDROID_PROCESS EQUAL 0)
+            if (ANDROID_PROCESS EQUAL 0 AND CMAKE_VERSION VERSION_GREATER "2.8")
                 set_property( CACHE ANDROID_SDK_TARGET PROPERTY STRINGS ${ANDROID_SDK_TARGETS} )
             endif()
             string(REGEX MATCH "[0-9]+$" ANDROID_SDK_TARGET_LEVEL "${ANDROID_SDK_TARGET}")

android/android.toolchain.cmake

@@ -172,7 +172,9 @@ if( EXISTS "${ANDROID_NDK}" )
 
  set( PossibleAndroidLevels "3;4;5;8;9" )
  set( ANDROID_API_LEVEL ${ANDROID_API_LEVEL} CACHE STRING "android API level" )
+ if( CMAKE_VERSION VERSION_GREATER "2.8")
   set_property( CACHE ANDROID_API_LEVEL PROPERTY STRINGS ${PossibleAndroidLevels} )
+ endif()
  
  if( NOT ANDROID_API_LEVEL GREATER 2 )
   set( ANDROID_API_LEVEL 8)
@@ -237,7 +239,9 @@ IF( NOT ARM_TARGET)
  set( ARM_TARGET armeabi-v7a )
 ENDIF()
 set( ARM_TARGET "${ARM_TARGET}" CACHE INTERNAL "the arm target for android, recommend armeabi-v7a for floating point support and NEON." )
-set_property( CACHE ARM_TARGET PROPERTY STRINGS ${PossibleArmTargets} )
+if( CMAKE_VERSION VERSION_GREATER "2.8")
+ set_property( CACHE ARM_TARGET PROPERTY STRINGS ${PossibleArmTargets} )
+endif()
 
 #set these flags for client use
 if( ARM_TARGET STREQUAL "armeabi" )