Added CCache support to Android build

To speed up rebuilds, define the NDK_CCACHE environment or CMake variable
to the path to your ccache binary. When declared, the android.cmake.toolchain
automatically uses CCache when compiling any C/C++ source file. For example:

export NDK_CCACHE=ccache

CMakeLists.txt

@@ -517,10 +517,10 @@ endif()
 status("")
 status("  C/C++:")
 status("    Built as dynamic libs?:" BUILD_SHARED_LIBS THEN YES ELSE NO)
-status("    C++ Compiler:"           CMAKE_COMPILER_IS_GNUCXX THEN "${CMAKE_CXX_COMPILER} (ver ${CMAKE_GCC_REGEX_VERSION})" ELSE "${CMAKE_CXX_COMPILER}" )
+status("    C++ Compiler:"           CMAKE_COMPILER_IS_GNUCXX THEN "${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} (ver ${CMAKE_GCC_REGEX_VERSION})" ELSE "${CMAKE_CXX_COMPILER}" )
 status("    C++ flags (Release):"    ${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_RELEASE})
 status("    C++ flags (Debug):"      ${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_DEBUG})
-status("    C Compiler:"             ${CMAKE_C_COMPILER})
+status("    C Compiler:"             ${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ARG1})
 status("    C flags (Release):"      ${CMAKE_C_FLAGS} ${CMAKE_C_FLAGS_RELEASE})
 status("    C flags (Debug):"        ${CMAKE_C_FLAGS} ${CMAKE_C_FLAGS_DEBUG})
 if(WIN32)

android/android.toolchain.cmake

@@ -187,6 +187,7 @@
 #     [+] updated for NDK r8b
 #     [~] all intermediate files generated by toolchain are moved into CMakeFiles
 #     [~] libstdc++ and libsupc are removed from explicit link libraries
+#     [+] added ccache support (via NDK_CCACHE environment or cmake variable)
 # ------------------------------------------------------------------------------
 
 cmake_minimum_required( VERSION 2.6.3 )
@@ -686,9 +687,25 @@ if( BUILD_WITH_ANDROID_NDK )
  endif()
 endif()
 
+# ccache support
+__INIT_VARIABLE( NDK_CCACHE ENV_NDK_CCACHE )
+if( NDK_CCACHE )
+ get_filename_component(NDK_CCACHE "${NDK_CCACHE}" ABSOLUTE)
+ set( NDK_CCACHE "${NDK_CCACHE}" CACHE PATH "The path to ccache binary" FORCE )
+else()
+ unset( NDK_CCACHE )
+endif()
+
 # specify the cross compiler
-set( CMAKE_C_COMPILER   "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc${TOOL_OS_SUFFIX}"     CACHE PATH "gcc" )
-set( CMAKE_CXX_COMPILER "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-g++${TOOL_OS_SUFFIX}"     CACHE PATH "g++" )
+if( NDK_CCACHE )
+ set( CMAKE_C_COMPILER   "${NDK_CCACHE}" CACHE PATH "ccache as C compiler" )
+ set( CMAKE_CXX_COMPILER "${NDK_CCACHE}" CACHE PATH "ccache as C++ compiler" )
+ set( CMAKE_C_COMPILER_ARG1 "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc${TOOL_OS_SUFFIX}"   CACHE PATH "gcc")
+ set( CMAKE_CXX_COMPILER_ARG1 "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-g++${TOOL_OS_SUFFIX}" CACHE PATH "g++")
+else()
+ set( CMAKE_C_COMPILER   "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc${TOOL_OS_SUFFIX}"    CACHE PATH "gcc" )
+ set( CMAKE_CXX_COMPILER "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-g++${TOOL_OS_SUFFIX}"    CACHE PATH "g++" )
+endif()
 set( CMAKE_ASM_COMPILER "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc${TOOL_OS_SUFFIX}"     CACHE PATH "Assembler" )
 if( CMAKE_VERSION VERSION_LESS 2.8.5 )
  set( CMAKE_ASM_COMPILER_ARG1 "-c" )
@@ -1039,7 +1056,9 @@ endmacro()
 # export toolchain settings for the try_compile() command
 if( NOT PROJECT_NAME STREQUAL "CMAKE_TRY_COMPILE" )
  set( __toolchain_config "")
- foreach( __var ANDROID_ABI ANDROID_FORCE_ARM_BUILD ANDROID_NATIVE_API_LEVEL ANDROID_NO_UNDEFINED ANDROID_SO_UNDEFINED ANDROID_SET_OBSOLETE_VARIABLES LIBRARY_OUTPUT_PATH_ROOT ANDROID_USE_STLPORT ANDROID_FORBID_SYGWIN ANDROID_NDK ANDROID_STANDALONE_TOOLCHAIN ANDROID_FUNCTION_LEVEL_LINKING __ndklibspath )
+ foreach( __var NDK_CCACHE ANDROID_ABI ANDROID_FORCE_ARM_BUILD ANDROID_NATIVE_API_LEVEL ANDROID_NO_UNDEFINED
+                ANDROID_SO_UNDEFINED ANDROID_SET_OBSOLETE_VARIABLES LIBRARY_OUTPUT_PATH_ROOT ANDROID_USE_STLPORT
+                ANDROID_FORBID_SYGWIN ANDROID_NDK ANDROID_STANDALONE_TOOLCHAIN ANDROID_FUNCTION_LEVEL_LINKING __ndklibspath )
   if( DEFINED ${__var} )
    if( "${__var}" MATCHES " ")
     set( __toolchain_config "${__toolchain_config}set( ${__var} \"${${__var}}\" CACHE INTERNAL \"\" )\n" )

cmake/OpenCVDetectCXXCompiler.cmake

@@ -54,11 +54,11 @@ endif()
 # Detect GNU version:
 # ----------------------------------------------------------------------------
 if(CMAKE_COMPILER_IS_GNUCXX)
-    execute_process(COMMAND ${CMAKE_CXX_COMPILER} --version
+    execute_process(COMMAND ${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} --version
                   OUTPUT_VARIABLE CMAKE_OPENCV_GCC_VERSION_FULL
                   OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-    execute_process(COMMAND ${CMAKE_CXX_COMPILER} -v
+    execute_process(COMMAND ${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} -v
                   ERROR_VARIABLE CMAKE_OPENCV_GCC_INFO_FULL
                   OUTPUT_STRIP_TRAILING_WHITESPACE)