message: cmake: don't overwrite flags, append it
diff: @@ -118,7 +118,7 @@ if(NOT IOS AND NOT ANDROID)
  add_definitions("-Wno-sign-compare")
  endif()
  - set(CMAKE_CXX_FLAGS_DEBUG "-DTESTING -DDEBUG")
  + set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DTESTING")
  add_executable(unit_tests_runner
  core/global_include_test.cpp
  