message: Enable CMake fo  subdirectory use
  Addresses issue where launch-c/launch-cxx is expected in CMAKE_BINARY_DIR
diff: @@ -74,18 +74,18 @@ if (CCACHE_PROGRAM)
  configure_file(build/launch-cxx.in launch-cxx)
  execute_process(COMMAND chmod a+rx
  - "${CMAKE_BINARY_DIR}/launch-c"
  - "${CMAKE_BINARY_DIR}/launch-cxx"
  + "${CMAKE_CURRENT_BINARY_DIR}/launch-c"
  + "${CMAKE_CURRENT_BINARY_DIR}/launch-cxx"
  )
  if (CMAKE_GENERATOR STREQUAL "Xcode")
  - set(CMAKE_XCODE_ATTRIBUTE_CC "${CMAKE_BINARY_DIR}/launch-c")
  - set(CMAKE_XCODE_ATTRIBUTE_CXX "${CMAKE_BINARY_DIR}/launch-cxx")
  - set(CMAKE_XCODE_ATTRIBUTE_LD "${CMAKE_BINARY_DIR}/launch-c")
  - set(CMAKE_XCODE_ATTRIBUTE_LDPLUSPLUS "${CMAKE_BINARY_DIR}/launch-cxx")
  + set(CMAKE_XCODE_ATTRIBUTE_CC "${CMAKE_CURRENT_BINARY_DIR}/launch-c")
  + set(CMAKE_XCODE_ATTRIBUTE_CXX "${CMAKE_CURRENT_BINARY_DIR}/launch-cxx")
  + set(CMAKE_XCODE_ATTRIBUTE_LD "${CMAKE_CURRENT_BINARY_DIR}/launch-c")
  + set(CMAKE_XCODE_ATTRIBUTE_LDPLUSPLUS "${CMAKE_CURRENT_BINARY_DIR}/launch-cxx")
  else()
  - set(CMAKE_C_COMPILER_LAUNCHER "${CMAKE_BINARY_DIR}/launch-c")
  - set(CMAKE_CXX_COMPILER_LAUNCHER "${CMAKE_BINARY_DIR}/launch-cxx")
  + set(CMAKE_C_COMPILER_LAUNCHER "${CMAKE_CURRENT_BINARY_DIR}/launch-c")
  + set(CMAKE_CXX_COMPILER_LAUNCHER "${CMAKE_CURRENT_BINARY_DIR}/launch-cxx")
  endif()
  endif()
  