Version bump to NJH21D

Change-Id: If7402e75597b8d24746e285ab8edefa0f1a37546
diff --git a/core/build_id.mk b/core/build_id.mk
index 43b7843..4c5ed3b 100644
--- a/core/build_id.mk
+++ b/core/build_id.mk
@@ -18,4 +18,4 @@
 # (like "CRB01").  It must be a single word, and is
 # capitalized by convention.
 
-export BUILD_ID=NJH21C
+export BUILD_ID=NJH21D