This patch enables building gcc-4.6.4 using gcc-2.95.3 and glibc-2.2.5

  * Tweak Makefile to allow overriding NATIVE_SYSTEM_HEADER_DIR using #:makeflags
  * Add missing limits.h include.
  * Add SSIZE_MAX define.  The SSIZE_MAX define has been added to Mes
    upstream and can be removed with the next Mes release.
  * Remove -fbuilding-libgcc flag, it assumes features being present from a
    newer gcc or glibc.
  * [MES_BOOTSTRAP_GCC]: Disable threads harder.

Upstream status: not presented upstream.

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index f3cc49fdb18..bc5718fc9a6 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -440,7 +440,7 @@ LINKER_PLUGIN_API_H = $(srcdir)/../include/plugin-api.h
 LTO_SYMTAB_H = $(srcdir)/../include/lto-symtab.h
 
 # Default native SYSTEM_HEADER_DIR, to be overridden by targets.
-NATIVE_SYSTEM_HEADER_DIR = /usr/include
+# NATIVE_SYSTEM_HEADER_DIR = /usr/include
 # Default cross SYSTEM_HEADER_DIR, to be overridden by targets.
 CROSS_SYSTEM_HEADER_DIR = @CROSS_SYSTEM_HEADER_DIR@
 
diff --git a/gcc/config/host-linux.c b/gcc/config/host-linux.c
index 94b7a0b89a7..ab2baab55ca 100644
--- a/gcc/config/host-linux.c
+++ b/gcc/config/host-linux.c
@@ -23,6 +23,12 @@
 #include "hosthooks.h"
 #include "hosthooks-def.h"
 
+// ../.././gcc/config/host-linux.c:213: `SSIZE_MAX' undeclared (first
+// use in this function)
+#include <limits.h>
+#ifndef	SSIZE_MAX
+# define SSIZE_MAX	LONG_MAX
+#endif
 
 /* Linux has a feature called exec-shield-randomize that perturbs the
    address of non-fixed mapped segments by a (relatively) small amount.
diff --git a/libgcc/generic-morestack-thread.c b/libgcc/generic-morestack-thread.c
index bbe6dd12b5a..1d1d48223d7 100644
--- a/libgcc/generic-morestack-thread.c
+++ b/libgcc/generic-morestack-thread.c
@@ -34,7 +34,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    will want to define inhibit_libc while building a compiler which
    can build glibc.  */
 
-#ifndef inhibit_libc
+#if 0 //!defined (inhibit_libc) && !MES_BOOTSTRAP_GCC
 
 #include <errno.h>
 #include <pthread.h>
