Enable R8 by default (second attempt for Q)

Fixed bugs which was discovered in the last attempt.

Bug: 74508478

Test: m -j PRODUCT-taimen-userdebug
Test: m -j PRODUCT-elfin-userdebug
Test: Check that some .vdex files built have R8 generated code

(cherry picked from commit a3b796d9981495bdca7e41b73e4a85d507856b58)

Change-Id: Ibe08137cd6db94b1fc487267e169d3f5ee598846
Merged-In: I2a8e0e5cad1d698ae73ba152e34a08a496112d7d
diff --git a/core/config.mk b/core/config.mk
index ec3c847..909b8b2 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -553,7 +553,7 @@
 
 # Default R8 behavior when USE_R8 is not specified.
 ifndef USE_R8
-  USE_R8 := false
+  USE_R8 := true
 endif
 
 #