Build and install the Testing Runtime APEX in ART device testing.

Replace the Debug Runtime APEX with the Testing Runtime APEX for ART
device testing.

This change does not change the behavior of ART device testing per se,
as test rules have not been updated (yet) to make use of the
additional files (ART gtests) included only in the Testing Runtime
APEX.

Test: ART (chroot-based) device testing
Bug: 129534335
Change-Id: I1b9dfcb9fe483584b4065908c1b2e24d19703b52
diff --git a/CleanSpec.mk b/CleanSpec.mk
index a9b086a..f59de64 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -82,6 +82,10 @@
 # Remove ART test target artifacts.
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/data/nativetest*/)
 
+# Remove all APEX artifacts after the change to use the Testing
+# Runtime APEX in lieu of the Debug Runtime APEX for ART testing.
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/apex)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************