Expands into an help string that looks pretty when the user executes
‘configure --help’. It is typically used in
(see External Software) or
AC_ARG_ENABLE (see Package Options). The following example makes this clearer.
[use foo (default is no)])],
The second argument of
not a literal, and should not be double quoted.
See Autoconf Language, for a more detailed explanation.
Then the last few lines of ‘configure --help’ appear like
--enable and --with options recognized:
--with-foo use foo (default is no)
AS_HELP_STRING macro is particularly helpful when the
left-hand-side and/or right-hand-side are composed of macro
arguments, as shown in the following example.
[AS_HELP_STRING([--with-$1], [use $1 (default is $2)])],