message: prevent cmake failure when no Fortran compiler is present.
  ADIOS2_USE_Fortran is "AUTO" by default, so even if no Fortran compiler
  was found, it'd still try to check a Fortran compiler flag, which failed
  without a Fortran compiler being enabled:
  CMake Error at /opt/local/share/cmake-3.19/Modules/Internal/CheckCompilerFlag.cmake:52 (message):
  check_compiler_flag: Fortran: needs to be enabled before use.
diff: @@ -372,7 +372,7 @@ include(CheckTypeRepresentation)
  #check_float_type_representation(double DOUBLE_TYPE_C)
  #check_float_type_representation("long double" LONG_DOUBLE_TYPE_C)
  -if(ADIOS2_USE_Fortran)
  +if(ADIOS2_HAVE_Fortran)
  #check_float_type_representation(real REAL_TYPE_Fortran LANGUAGE Fortran)
  #check_float_type_representation("real(kind=4)" REAL4_TYPE_Fortran LANGUAGE Fortran)
  #check_float_type_representation("real(kind=8)" REAL8_TYPE_Fortran LANGUAGE Fortran)
  