I took your email address from the libpopt source code makefile.
./config.sub [OPTION] ALIAS
Canonicalize a configuration name.
Operation modes:
-h, --help print this help, then exit
-t, --time-stamp print date of last modification, then exit
-v, --version print version number, then exit
Otherwise make fail to compile. Perhaps this is an error from your Makefile formatting ?
Cheers,
Simon