From 11223957d1f797ca940934c3ae7407ffacb84ca3 Mon Sep 17 00:00:00 2001
From: dzy <daizy15@mails.tsinghua.edu.cn>
Date: Fri, 14 Sep 2018 20:05:59 +0800
Subject: [PATCH] Add `mkdir build` in makefile.

It this is missing, building with a clean repository will fail
because build/ does not exist.
---
 kernel/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/Makefile b/kernel/Makefile
index 1213feb..5e58276 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -143,6 +143,7 @@ $(kernel): kernel $(assembly_object_files) $(linker_script)
 		$(assembly_object_files) target/x86_64-blog_os/$(mode)/libucore.a
 
 kernel:
+	@mkdir build/$(arch) -p
 	@CC=$(cc) cargo xbuild $(build_args)
 
 # compile assembly files