message: revert extra apple guard
diff: @@ -121,13 +121,6 @@ if(C_COMPILER_FAMILY_IS_CLANG AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 3.
  set(clang_unused_local_typedef "-Wno-unused-local-typedefs")
  endif()
  -# X-Code 9 + apple clang 9 are based of llvm 4.0, so we need this flag.
  -# For whatever reason C_COMPILER_FAMILY_IS_CLANG isn't true this case.
  -if(APPLE AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 9.0))
  -
  - set(clang_unused_local_typedef "-Wno-unused-local-typedefs")
  -endif()
  -
  blt_append_custom_compiler_flag(FLAGS_VAR AXOM_DISABLE_UNUSED_LOCAL_TYPEDEF
  DEFAULT " "
  CLANG "${clang_unused_local_typedef}"
  