util/kconfig: Uprev to Linux 5.13's kconfig

This was originally several commits that had to be squashed into one
because the intermediate states weren't able to build coreboot:

 - one to remove everything that wasn't our own code, leaving only
   regex.[ch], toada.c, description.md and Makefile.inc.
 - one to copy in Linux 5.13's scripts/kconfig and adapt Makefile.inc
   to make the original Makefile work again.
 - adapt abuild to use olddefconfig, simplifying matters.
 - apply patches in util/kconfig/patches.
 - Some more adaptations to the libpayload build system.

The patches are now in util/kconfig/patches/, reverse applying them
should lead to a util/kconfig/ tree that contains exactly the Linux
version + our own 5 files.

Change-Id: Ia0e8fe4e9022b278f34ab113a433ef4d45e5c355
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37152
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

util/kconfig/gconf-cfg.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+PKG="gtk+-2.0 gmodule-2.0 libglade-2.0"
+
+if [ -z "$(command -v pkg-config)" ]; then
+	echo >&2 "*"
+	echo >&2 "* 'make gconfig' requires 'pkg-config'. Please install it."
+	echo >&2 "*"
+	exit 1
+fi
+
+if ! pkg-config --exists $PKG; then
+	echo >&2 "*"
+	echo >&2 "* Unable to find the GTK+ installation. Please make sure that"
+	echo >&2 "* the GTK+ 2.0 development package is correctly installed."
+	echo >&2 "* You need $PKG"
+	echo >&2 "*"
+	exit 1
+fi
+
+if ! pkg-config --atleast-version=2.0.0 gtk+-2.0; then
+	echo >&2 "*"
+	echo >&2 "* GTK+ is present but version >= 2.0.0 is required."
+	echo >&2 "*"
+	exit 1
+fi
+
+echo cflags=\"$(pkg-config --cflags $PKG)\"
+echo libs=\"$(pkg-config --libs $PKG)\"