It sounds like you're puzzling with Gnu make options used with your FORTRAN compiler:
1. As you know, you "compile" source code into an executable program.
Specifically, you "compile" .f source files into .o "object" files, then "link" all the objects you've built (along with system libraries you need) into your program image. I'm sure you already know all this...
2. If you're compiling on a PC (for example), you'll usually create object files and executables that can run on your PC.
This isn't a requirement, however.
You could just as easily compile objects that can run on another, *different* architecture (like an ARM processor, or a MIPS CPU, or anything imaginable. This is called "cross compiling". Generating an executable for another, different platform is called "cross-linking".
3. When you "build" a program, you typically use a tool that automates the busy work for you. This tool might be a graphical IDE (like Visual Studio, for example). Or it might be "make".
The tool might just call the compiler and linker, or it might also invoke other tools, like source control checkout or unit testing.
Gnu make supports all of these different options with special variables like "GFLAGS" or "OFLAGS". You can read about them here:
'Hope that helps .. PSM