message: ENH: only add flags when using ninja.
diff: @@ -161,12 +161,15 @@ blt_append_custom_compiler_flag(FLAGS_VAR CMAKE_CXX_FLAGS_DEBUG
  CLANG "-fstandalone-debug"
  )
  -blt_append_custom_compiler_flag(FLAGS_VAR CMAKE_CXX_FLAGS
  +blt_append_custom_compiler_flag(FLAGS_VAR AXOM_NINJA_FLAGS
  DEFAULT " "
  GNU "-fdiagnostics-color=always"
  CLANG "-fcolor-diagnostics"
  )
  +if( ${CMAKE_MAKE_PROGRAM} STREQUAL "ninja" OR ${CMAKE_MAKE_PROGRAM} MATCHES ".*/ninja$" )
  + set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${AXOM_NINJA_FLAGS}")
  +endif()
  # message(STATUS "Custom compiler flags:")
  # foreach(flag ${custom_compiler_flags_list})
  