tools/Unix.mk: allow defconfig to overwrite old config

When using include command in defconfig, it is necessary to support overwriting the configuration in other files

kconfig-conf only prints warnings, but does not return errors

Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>

tools/Unix.mk

@@ -657,7 +657,9 @@ define kconfig_tweak_disable
 	kconfig-tweak --file $1 -u $2
 endef
 else
-  KCONFIG_WARNING  = 2> >(tee kwarning) | cat && if [ -s kwarning ]; \
+  OVERWRITE_WARNING = "set more than once"
+  KCONFIG_WARNING   = 2> >(grep -v ${OVERWRITE_WARNING} | tee kwarning) | \
+                                                  cat && if [ -s kwarning ]; \
                                                   then rm kwarning; \
                                                   exit 1; \
                                                  else \