The executable depends on the library specified (/usr/local/lib/libg2c.0.dylib).
On Linux you can specify a "-static" flag to build an executable which isn't dependant on any libraries, but this doesn't work on Mac OS X.
So one possible solution is to either install G77 on each Mac you want to run your program, or at the very least install /usr/local/lib/libg2c.0.dylib.