[patch, docs] RFC: Document --enable-stage1-languages configure option.

[Brooks Moses <brooks dot moses at codesourcery dot com>]

I was just looking for documentation for the --enable-stage1-languages 
configure option, and realized that it doesn't exist.  So this patch 
documents it.

Since this was something that I was looking for documentation on, I'm 
not sure if I've got things right or not, and whether there are 
important bits left out, and I suspect some of this could be written 
better.  Thus, I'd appreciate comments on this.

------------------------------------------------------------------
2007-01-28  Brooks Moses  <brooks.moses@codesourcery.com>

	PR 30635
	* doc/install.texi: Document --enable-stage1-languages

------------------------------------------------------------------

Thanks!
- Brooks

Index: gcc/doc/install.texi
===================================================================
--- gcc/doc/install.texi	(revision 121319)
+++ gcc/doc/install.texi	(working copy)
@@ -1131,6 +1131,9 @@
 work anymore, as those language sub-directories might not have been
 configured!
 
+@item --enable-stage1-languages=@var{lang1},@var{lang2},@dots{}
+Specify that particular set of compilers and their runtime libraries should be built with the system C compiler during stage 1 of the bootstrap process, rather than with the bootstrapped C compiler.  The list of valid values is the same as for @option{--enable-languages}; the option @code{all} will build all of the languages enabled by @option{--enable-languages} at stage 1.  This option is primarily useful for GCC development; for instance, it can be useful in determining if a non-C failure is due to a bug in the front end or is due to a bug in the C compiler that is causing the front end to be miscompiled.
+
 @item --disable-libada
 Specify that the run-time libraries and tools used by GNAT should not
 be built.  This can be useful for debugging, or for compatibility with