GNU Make build example

[mathstuf]

There are patches to GNU Make to support GCC's module mapper socket. Example code for using it would be nice to have.

@urnathan

[johan-boule]

There's something mysterious about why Nathan chose to first implement modules support in a repo that describes itself as a pure port of GNU Make to Amiga and SAS/C.
EDIT: Now I understand... It's because README.Amiga appears first alphabetically.