If your usage message is in app_name.use, where
app_name is your executable name, add a # character at the
start of the USEFILE line. This lets the recursive
Makefile system automatically pick up your usage message.
If your
usage message is in a file with a different name, or you want to explicitly specify your usage
message's file name, change the USAGE line as follows:
USAGE=$(PROJECT_ROOT)/
usage_message.use
where usage_message.use is the name of the file containing your usage
message. This also assumes that your usage message file is in the root of the project
directory. If the usage message file is located in another directory, include it instead of
$(PROJECT_ROOT).