kconfig: make oldconfig work "non-strict"

oldconfig is regularly used to clean up templates that sometimes contain
duplicates or old symbols.
Since it cleans up the config, it doesn't need to fail on issues.

Change-Id: Ife0e9e3b9bfdde1eb6be0e2e38e81b9042cb7950
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/13687
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/util/kconfig/Makefile b/util/kconfig/Makefile
index a7d3855..ffd5253 100644
--- a/util/kconfig/Makefile
+++ b/util/kconfig/Makefile
@@ -34,8 +34,10 @@
 nconfig: $(objk)/nconf
 	$< $(Kconfig)
 
+# Disable strict mode because oldconfig is typically used to clean up
+# templates and the like. The second invocation should already have sane data.
 oldconfig: $(objk)/conf
-	$< --$@ $(Kconfig)
+	KCONFIG_STRICT= $< --$@ $(Kconfig)
 	$< --silentoldconfig $(Kconfig)
 
 silentoldconfig: $(objk)/conf