fix build id for master branch

Bug: 16304509
Change-Id: I2858e20701d3e705e46bd6b4f70345457b1ef90f
diff --git a/core/build_id.mk b/core/build_id.mk
index dd02025..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=LDW13B
+export BUILD_ID=MASTER