message: cmake enable CCACHE in build
diff: @@ -8,6 +8,25 @@ cmake_policy(SET CMP0025 NEW)
  project(dronecode_sdk)
  +# ccache
  +option(CCACHE "Use ccache if available" ON)
  +find_program(CCACHE_PROGRAM ccache)
  +if (CCACHE AND CCACHE_PROGRAM AND NOT DEFINED ENV{CCACHE_DISABLE})
  +
  + get_filename_component(ccache_real_path ${CCACHE_PROGRAM} REALPATH)
  + get_filename_component(cxx_real_path ${CMAKE_CXX_COMPILER} REALPATH)
  + get_filename_component(cxx_abs_path ${CMAKE_CXX_COMPILER} ABSOLUTE)
  +
  + if ("${ccache_real_path}" STREQUAL "${cxx_real_path}")
  + message(STATUS "ccache enabled via symlink (${cxx_abs_path} -> ${cxx_real_path})")
  + else()
  + message(STATUS "ccache enabled (export CCACHE_DISABLE=1 to disable)")
  + set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_PROGRAM}")
  + endif()
  +
  +endif()
  +
  +
  option(BUILD_TESTS "Build tests" ON)
  include(cmake/compiler_flags.cmake)
  