Revert "Use prebuilts of the ART Module by default."

This reverts commit efab03ff61297fadb303170fdf728e3324bfde2f.

Reason for revert: Breaks sc-dev builds.

Merged-In set to http://ag/15107826 to avoid merging downstream.

Bug: 192558747
Change-Id: Id17caafee41b5aed65b5b294c729a548379aa41a
Merged-In: I8990b726affeb08eabf130d20be45129a7c1c58d
diff --git a/core/android_soong_config_vars.mk b/core/android_soong_config_vars.mk
index 41cf7b6..04a055d 100644
--- a/core/android_soong_config_vars.mk
+++ b/core/android_soong_config_vars.mk
@@ -61,7 +61,7 @@
   # This sets the default for building ART APEXes from source rather than
   # prebuilts (in packages/modules/ArtPrebuilt and prebuilt/module_sdk/art) in
   # all other platform builds.
-  SOONG_CONFIG_art_module_source_build ?= false
+  SOONG_CONFIG_art_module_source_build ?= true
 endif
 
 # Apex build mode variables