sdk: clean scripts/config before packing tarball (FS#504)

Avoids shipping potentially incompatible object files and also reduces
the tarball size

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/sdk/Makefile

@@ -137,6 +137,7 @@ $(BIN_DIR)/$(SDK_NAME).tar.xz: clean
 	find $(SDK_BUILD_DIR) -name .git | $(XARGS) rm -rf
 	find $(SDK_BUILD_DIR) -name .svn | $(XARGS) rm -rf
 	find $(SDK_BUILD_DIR) -name CVS | $(XARGS) rm -rf
+	-make -C $(SDK_BUILD_DIR)/scripts/config clean
 	(cd $(BUILD_DIR); \
 		tar -I 'xz -7e' -cf $@ $(SDK_NAME); \
 	)