ART: Fix the debug-build inclusion

Should be TARGET_BUILD_VARIANT.

Bug: 62087184
Test: m
Change-Id: Ia386ba1f883bbd22cd867e054882410c263b373c
diff --git a/Android.mk b/Android.mk
index 0402513..a4473f5 100644
--- a/Android.mk
+++ b/Android.mk
@@ -380,11 +380,12 @@
 # * We will never add them if PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD = false.
 # * We will always add them if PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD = true.
 # * Otherwise, we will add them by default to userdebug and eng builds.
-ifneq (false,$(PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD))
-ifneq (,$(filter userdebug eng,$(PRODUCT_TARGET_BUILD_VARIANT)))
-  PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD := true
+art_target_include_debug_build := $(PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD)
+ifneq (false,$(art_target_include_debug_build))
+ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
+  art_target_include_debug_build := true
 endif
-ifeq (true,$(PRODUCT_ART_TARGET_INCLUDE_DEBUG_BUILD))
+ifeq (true,$(art_target_include_debug_build))
 LOCAL_REQUIRED_MODULES += \
     libartd \
     libartd-compiler \