Version bump to OPR6.170623.021

Change-Id: Ieb8308add403bcb6237f2c703951613e061cdc85
diff --git a/core/build_id.mk b/core/build_id.mk
index b76b84d..75bc3c8 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=OPR6.170623.020
+export BUILD_ID=OPR6.170623.021