Update git submodules

* Update kernel/build from branch 'master'
  to 23c16f4dc9c2b9805f26f6dcc620775a212d7578
  - build.sh: Fix missing quotes on -n check
    
    Without the quotes -n always returns true. Add them.
    
    Bug: 176930600
    Fixes: 80db273b7278 ("build.sh: add support for AVB signing")
    Signed-off-by: Will McVicker <willmcvicker@google.com>
    Change-Id: I7f5b59638dbff718e2377586b6a59dd2531b75fd
    
diff --git a/kernel/build b/kernel/build
index 80db273..23c16f4 160000
--- a/kernel/build
+++ b/kernel/build
@@ -1 +1 @@
-Subproject commit 80db273b727847db7bf87a9293c1c9ea6ec51216
+Subproject commit 23c16f4dc9c2b9805f26f6dcc620775a212d7578