- a partial selection from https://github.com/mrklein/openfoam-os-x
  with adjustments. The primary purpose is to reduce header-level
  incompatibilities and to provide a common set of make rules to allow
  easier patching (or re-integration).

- initial settings for ADIOS2, linuxARM64Gcc, linuxARM64Clang

- the cray C/C++ compilers appear to be option-compatible with gcc.

- no wmake rules for 32bit builds (deemed to be unnecessary)