FP2-84: remove the default build id

In default, the build id was defined in build/core/build_id.mk, so we should remove it.

Change-Id: Id02fe50e4ba20b3d90558bbd3fa4780573d69210
diff --git a/core/build_id.mk b/core/build_id.mk
index 1ade542..c666f7e 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=LRX22G
+#export BUILD_ID=LRX22G