message: Fix build error seen in CI
diff: @@ -23,7 +23,11 @@ include(ExternalProject)
  include(CMakeDependentOption)
  include(cmake/sdl.cmake)
  +if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
  + set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wno-comment -Wno-sign-compare")
  +elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wno-comment -Wno-sign-compare -Wbackslash-newline-escape")
  +endif()
  # In order to compile ngraph-tf with memory leak detection, run `cmake` with `-DCMAKE_BUILD_TYPE=Sanitize`.
  # N.B.: This *will* crash python unit tests because ngraph-tf will be loaded "too late" via `dlopen`,
  