configureconfigure uses some other scripts to help in its work:
config.sub and config.guess
files, kept in the top level directory, are used. FIXME: when is the
config.guess file in the gcc directory (that just calls
the top level one) used?
config.gcc is used to handle configuration
specific to the particular build, host or target machine. (In
general, this should only be used for features that cannot reasonably
be tested in Autoconf feature tests.) See The config.gcc File, for details of the contents of this file.
/config-lang.in that is used for
front-end-specific configuration. See The Front End config-lang.in File, for details of this file.
configure.frag is used as part of
creating the output of configure.