CMake: Make sure to find OpenMP dependency before usage.

[MehdiChinoune]

cmake will throw an error if OpenMP::OpenMP_C or OpenMP::OpenMP_Fortran were not found first. see: msys2/MINGW-packages#24616

[MehdiChinoune]

There are two issues:

• NOFORTRAN is not a Boolean variable, need to be changed so it could be replaced by ON or OFF.
  I see that it is set to 2 in one place but never tested with that value, all conditionals are 'if(NOFORTRAN)' or 'if(NOT NOFORTRAN)'
• CMake couldn't find OpenMP Fortran component without a Fortran compiler, so the user has to install one which is a little annoying giving that no Fortran code is going to be compiled.

[martin-frbg]

NOFORTRAN used to be tri-state (something like "the user wanted it but the compiler doesn't work" IIRC) I'll take a look as soon as I can. CMake macro features are elegant but they bring in so many new logical dependencies compared to a naive gmake build ...