util/kconfig: Uprev to Linux 6.2's kconfig

The upstream build system uses a newly introduced function `read-file`,
so copy that in from Linux 6.2.

TEST=`util/abuild/abuild -C` output (config.h and config.build) remains
the same

Change-Id: Ic100bf189ebd3eaa0eb26904ae8602910329a180
Signed-off-by: Patrick Georgi <patrick@coreboot.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79179
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

util/kconfig/gconf-cfg.sh

@@ -1,6 +1,9 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 
+cflags=$1
+libs=$2
+
 PKG="gtk+-2.0 gmodule-2.0 libglade-2.0"
 
 if [ -z "$(command -v ${HOSTPKG_CONFIG})" ]; then
@@ -26,5 +29,5 @@ if ! ${HOSTPKG_CONFIG} --atleast-version=2.0.0 gtk+-2.0; then
 	exit 1
 fi
 
-echo cflags=\"$(${HOSTPKG_CONFIG} --cflags $PKG)\"
-echo libs=\"$(${HOSTPKG_CONFIG} --libs $PKG)\"
+${HOSTPKG_CONFIG} --cflags ${PKG} > ${cflags}
+${HOSTPKG_CONFIG} --libs ${PKG} > ${libs}