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/patches/0011-remove-include-config-hardcodes.patch

@@ -0,0 +1,39 @@
+Index: kconfig/confdata.c
+===================================================================
+--- kconfig.orig/confdata.c
++++ kconfig/confdata.c
+@@ -241,6 +241,13 @@ static const char *conf_get_autoconfig_n
+ 	return name ? name : "include/config/auto.conf";
+ }
+ 
++static const char *conf_get_autobase_name(void)
++{
++	char *name = getenv("KCONFIG_SPLITCONFIG");
++
++	return name ? name : "include/config/";
++}
++
+ static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
+ {
+ 	char *p2;
+@@ -1024,7 +1031,7 @@ static int conf_touch_deps(void)
+ 	struct symbol *sym;
+ 	int res, i;
+ 
+-	strcpy(depfile_path, "include/config/");
++	strcpy(depfile_path, conf_get_autobase_name());
+ 	depfile_prefix_len = strlen(depfile_path);
+ 
+ 	name = conf_get_autoconfig_name();
+@@ -1102,7 +1109,10 @@ int conf_write_autoconf(int overwrite)
+ 	if (!overwrite && is_present(autoconf_name))
+ 		return 0;
+ 
+-	conf_write_dep("include/config/auto.conf.cmd");
++	char autoconfcmd_path[PATH_MAX];
++	snprintf(autoconfcmd_path, sizeof(autoconfcmd_path), "%s%s",
++		conf_get_autobase_name(), "auto.conf.cmd");
++	conf_write_dep(autoconfcmd_path);
+ 
+ 	if (conf_touch_deps())
+ 		return 1;