[PATCH, doc] PR30739: awk is a build prerequisite

[Ralf Wildenhues <Ralf.Wildenhues@gmx.de>]

I suppose nobody in those PRs (30739, 29049) remembers which gawk
versions were broken, so let's just go for a general mention.

According to 'info gawk SVR4', GCC needs at least SVR4 awk because
multiple -f options, -v, and regex constants are used during the build.
I haven't seen any Posix requirement in the scripts, at a quick glance.

Tested 'make html info pdf'.  OK for trunk?

Thanks,
Ralf

gcc/ChangeLog:
2008-06-14  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>

	PR documentation/30739
        * doc/install.texi (Prerequisites): Document dependency on awk.

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 127f065..50b135d 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -273,6 +273,12 @@ environment to your ``good'' shell prior to running
 @command{zsh} is not a fully compliant POSIX shell and will not
 work when configuring GCC@.
 
+@item A ``working'' SVR4 or POSIX awk
+
+Necessary for creating some of the generated source files for GCC@.
+If in doubt, use a recent GNU awk version, as some of the older ones
+are broken.
+
 @item GNU binutils
 
 Necessary in some circumstances, optional in others.  See the