make: Makefile Arguments

 
 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 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 (SeeWriting
 Makefiles Makefiles.).