fix build id

Bug: 15264432

Change-Id: Ib937af1401a18e67a3dbac471c21231ebd9e3c85
(cherry picked from commit 44e1b0bd8a4085f7fb5ac124ad4d55228aa4f98d)
diff --git a/core/build_id.mk b/core/build_id.mk
index 1a93148..0e8e2cf 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=AAV52B
+export BUILD_ID=MASTER