Define a "Fortran_FORMAT" target and source file property. Initialize
the target property from a "CMAKE_Fortran_FORMAT" variable. Interpret
values "FIXED" and "FREE" to indicate the source file format. Append
corresponding flags to the compiler command line.
The Cray Fortran compiler needs "-em" to enable module output and also
"-J." to place the .mod files in the current working directory (instead
of next to the .o file).