message: Fix name of 'macOS' and add asteriks to brands, NFC.
diff: @@ -194,7 +194,7 @@ Optional Features
  **LIBOMP_OMPT_SUPPORT** = ``ON|OFF``
  Include support for the OpenMP Tools Interface (OMPT).
  This option is supported and ``ON`` by default for x86, x86_64, AArch64, and
  - PPC64 on Linux, Windows, and mac OS.
  + PPC64 on Linux*, Windows*, and macOS*.
  This option is ``OFF`` if this feature is not supported for the platform.
  **LIBOMP_OMPT_OPTIONAL** = ``ON|OFF``
  