Sync toplevel with upstream GCC.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

include/environ.h

@@ -0,0 +1,33 @@
+/* Declare the environ system variable.
+   Copyright (C) 2015 Free Software Foundation, Inc.
+
+This file is part of the libiberty library.
+Libiberty is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public
+License as published by the Free Software Foundation; either
+version 2 of the License, or (at your option) any later version.
+
+Libiberty is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with libiberty; see the file COPYING.LIB.  If not,
+write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
+Boston, MA 02110-1301, USA.  */
+
+/* On OSX, the environ variable can be used directly in the code of an
+   executable, but cannot be used in the code of a shared library (such as
+   GCC's liblto_plugin, which links in libiberty code).  Instead, the
+   function _NSGetEnviron can be called to get the address of environ.  */
+
+#ifndef HAVE_ENVIRON_DECL
+#  ifdef __APPLE__
+#     include <crt_externs.h>
+#     define environ (*_NSGetEnviron ())
+#  else
+extern char **environ;
+#  endif
+#  define HAVE_ENVIRON_DECL
+#endif