doc: document --build and cross-compilation better

* doc/autoconf.texi (Specifying Target Triplets): Mention that
specifying a build-type that differs from host-type enables
cross-compilation.  Problem reported by Bruno Haible in:
http://lists.gnu.org/archive/html/autoconf-patches/2012-04/msg00009.html

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 2ae8bb933d3549c97e500d544d12bb376bf0b1c1..b1295ebe5873b496eaa38f5e3aa6e85ed50e2c9d 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -21747,10 +21747,12 @@ system types are involved.  The options to specify them are:
 @item --build=@var{build-type}
 the type of system on which the package is being configured and
 compiled.  It defaults to the result of running @command{config.guess}.
+Specifying a @var{build-type} that differs from @var{host-type} enables
+cross-compilation mode.
 
 @item --host=@var{host-type}
 the type of system on which the package runs.  By default it is the
-same as the build machine.  Specifying it enables the cross-compilation
+same as the build machine.  Specifying it enables cross-compilation
 mode.
 
 @item --target=@var{target-type}