util/kconfig: Move coreboot specific changes into Makefile.inc

This eases maintenance of our kconfig fork.

Change-Id: Ia4bc0bf22e66457356b9f8fcbea9412792495bca
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37151
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/kconfig/Makefile.inc

@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Early configuration of coreboot specific changes
+Kconfig ?= src/Kconfig
+
+# Include verbatim Makefile
+include $(dir $(lastword $(MAKEFILE_LIST)))Makefile
+
+# Extend Linux kconfig build rules
+
+# Support mingw by shipping our own regex implementation
+_OS=$(shell uname -s |cut -c-7)
+regex-objs=
+ifeq ($(_OS),MINGW32)
+	regex-objs=regex.o
+endif
+$(objk)/regex.o: $(srck)/regex.c
+	$(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) -DHAVE_STRING_H -c -o $@ $<
+
+conf-objs += $(regex-objs)
+mconf-objs += $(regex-objs)
+
+# Provide tool to convert kconfig output into Ada format
+$(objk)/toada: $(objk)/toada.o
+	$(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) -o $@ $^
+$(objk)/toada.o: $(srck)/toada.c
+	$(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) -c -o $@ $<