message: [c++] Suppress Comm codegen when Comm not enabled
diff: @@ -5,9 +5,13 @@ set (core_schemas
  set (schemas)
  list (APPEND schemas ${core-schemas})
  +if (BOND_ENABLE_COMM)
  + set(comm-flag COMM)
  +endif()
  +
  add_bond_codegen (${core_schemas}
  ENUM_HEADER
  - COMM
  + ${comm-flag}
  OUTPUT_DIR ${BOND_GENERATED}/bond/core)
  # Generate again into intermediate dir so that we can build libraries
  @@ -19,7 +23,7 @@ add_bond_codegen (${core_schemas}
  # in a clean build, leading to collisions in multi-processor build.
  add_bond_codegen (${core_schemas}
  ENUM_HEADER
  - COMM
  + ${comm-flag}
  OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bond/core)
  file (GLOB core_headers "inc/bond/core/*.h")
  