Various C projects provide a 'make help' target. Our root directory
does so. The roms/ directory lacks a such rule, but already displays
a help output when the default target is called.
Add a 'help' target aliased to the default one, to avoid:
$ make -C roms help
make: *** No rule to make target 'help'. Stop.
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190920171159.18633-1-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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