9.1 Arguments to Specify the Makefile
The way to specify the name of the makefile is with the `-f' or
`--file' option (`--makefile' also works). For example,
`-f altmake' says to use the file `altmake' as the makefile.
If you use the `-f' flag several times and follow each `-f'
with an argument, all the specified files are used jointly as
If you do not use the `-f' or `--file' flag, the default is
to try `GNUmakefile', `makefile', and `Makefile', in
that order, and use the first of these three which exists or can be made
(see section Writing Makefiles).