Revert "Enable R8 by default (second attempt)"

This reverts commit f2a697725ccb0f6c1fa0cd96568f1bc9009890e2.

Reason for revert: b/70710434

Change-Id: Ia6d42e4c2fc7e7a4ca67d42d7aaa57ab95c2cc9a
diff --git a/core/config.mk b/core/config.mk
index d81709e..e43793a 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -546,7 +546,7 @@
 
 # Default R8 behavior when USE_R8 is not specified.
 ifndef USE_R8
-  USE_R8 := true
+  USE_R8 := false
 endif
 
 #