http://sourceware.org/ml/libc-alpha/2007-03/msg00017.html:

GCC trunk now has multiple internal headers directories, one
containing the self-contained GCC-provided headers and one containing
the <limits.h> (not self-contained but including libc's <limits.h> or
a fixed version thereof) and the fixed headers; more such directories
may be added in future.

When glibc uses -nostdinc, it needs to use -isystem options for all
these internal directories.  This patch teaches it about the
include-fixed directory (and is harmless with old GCC versions without
that directory).

2007-03-18  Joseph Myers  <joseph@codesourcery.com>

	* configure.in: Also pass -isystem option for GCC's include-fixed
	directory.
	* configure: Regenerate.

Index: configure.in
===================================================================
--- /tmp/configure.in	2008-04-05 19:20:52.176759390 +0200
+++ glibc-2.6.1/configure.in	2008-04-05 19:21:26.663424600 +0200
@@ -912,7 +912,7 @@
 # thing on a system that doesn't need fixincludes.  (Not presently a problem.)
 if test -n "$sysheaders"; then
   ccheaders=`$CC -print-file-name=include`
-  SYSINCLUDES="-nostdinc -isystem $ccheaders \
+  SYSINCLUDES="-nostdinc -isystem $ccheaders -isystem $ccheaders-fixed \
 -isystem `echo $sysheaders | sed 's/:/ -isystem /g'`"
   if test -n "$CXX"; then
     cxxversion=`$CXX -dumpversion 2>&AS_MESSAGE_LOG_FD` &&