fix out-of-source-tree build

Makefile

@@ -760,7 +760,7 @@ PHONY += prepare-all
 # 2) Create the include2 directory, used for the second asm symlink
 prepare3: .kernelrelease
 ifneq ($(KBUILD_SRC),)
-	@echo '  Using $(srctree) as source for kernel'
+	@echo '  Using $(srctree) as source for busybox'
 	$(Q)if [ -f $(srctree)/.config ]; then \
 		echo "  $(srctree) is not clean, please run 'make mrproper'";\
 		echo "  in the '$(srctree)' directory.";\

applets/usage.c

@@ -1,7 +1,9 @@
 /* vi: set sw=4 ts=4: */
 #include <unistd.h>
 
-#include "autoconf.h"
+/* Just #include "autoconf.h" doesn't work for builds in separate
+ * object directory */
+#include "../include/autoconf.h"
 
 static const char usage_messages[] = ""
 #define MAKE_USAGE