make: Makefile Arguments
9.1 Arguments to Specify the Makefile
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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 (Writing
Makefiles Makefiles.).