message: construction_worker: adjusted flags for Clang sanitizer
  we are overrding the CXXFLAGS provided by travis in order to use gcc's libstdc++
diff: @@ -5,7 +5,7 @@ option(JSON_NoExceptions "Build test suite without exceptions" OFF)
  if(JSON_Sanitizer)
  message(STATUS "Building test suite with Clang sanitizer")
  if(NOT MSVC)
  - set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -O2 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer")
  + set(CMAKE_CXX_FLAGS "-g -O2 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer")
  endif()
  endif()
  