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
makefiles.
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 Writing Makefiles).