Version bump to SD1A.210817.019.C4 [core/build_id.mk]

Change-Id: Ib405a22db0c04f26f68a5a43cfae050897c42e93

core/build_id.mk

diff --git a/core/build_id.mk b/core/build_id.mk
index 535d49d..d766fb3 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.
 
-BUILD_ID=SD1A.210817.019.C3
+BUILD_ID=SD1A.210817.019.C4