Version bump to OPM4.171019.021

Change-Id: Ie7bf8220388f0221557f1b3145c90b575de88331
diff --git a/core/build_id.mk b/core/build_id.mk
index 5fb6c5a..f4c6477 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=OPM4.171019.020
+export BUILD_ID=OPM4.171019.021