Version bump to OPD3.170816.021

Change-Id: Icea34f73bd87a90c77493acd8a32c3819014dcfa
diff --git a/core/build_id.mk b/core/build_id.mk
index d7f5a5e..5b7719a 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=OPD3.170816.020
+export BUILD_ID=OPD3.170816.021