[FAB-11242] Add build/ into gitignore

Now when doing build, there will generate a build/ path.

This should not be included into git consideration.

Change-Id: I784d8ab23ea352040adbc467ff9d283d5f4e3d83
Signed-off-by: Baohua Yang <yangbaohua@gmail.com>

Author: yeasy

.gitignore

@@ -13,6 +13,7 @@ tags
 .tags
 .vagrant/
 /.build
+build/
 /release/darwin-amd64
 /release/linux-amd64
 /release/linux-s390x