Update build_id.mk and version_defaults.mk for SC V2

Set BUILD_ID to "SC_V2".

Bug: 201082421
Test: m checkbuild
Merged-In: I39a82c8ac3fd0b43bad06ec47b85aaeda6ef5cb4
Change-Id: Ie8bed4cefed83db5324ad98b6e70cb69b3f82780
diff --git a/core/build_id.mk b/core/build_id.mk
index 2f9c3f3..eee184e 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=MASTER
+BUILD_ID=SC_V2