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14 Manual Configuration
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A few kinds of features can't be guessed automatically by running test
programs.  For example, the details of the object-file format, or
special options that need to be passed to the compiler or linker.
Autoconf provides a uniform method for handling unguessable features, by
giving each operating system a “canonical system type”, also known as a
“canonical name” or “target triplet”.

   If you use any of the macros described in this chapter, you must
distribute the helper scripts ‘config.guess’ and ‘config.sub’ along with
your source code.  Some Autoconf macros use these macros internally, so
you may need to distribute these scripts even if you do not use any of
these macros yourself.  *Note Input::, for information about the
‘AC_CONFIG_AUX_DIR’ macro which you can use to control in which
directory ‘configure’ looks for helper scripts, and where to get the
scripts from.

* Menu:

* Specifying Target Triplets::  Specifying target triplets
* Canonicalizing::              Getting the canonical system type
* Using System Type::           What to do with the system type