Do not use $? in recipe

Kati cannot support this automatic variable as ninja doesn't
have a feature for this.

Change-Id: Ie9130c31916954454eb201129ae6f49554453586
diff --git a/build/Android.oat.mk b/build/Android.oat.mk
index 592843e..50600ef 100644
--- a/build/Android.oat.mk
+++ b/build/Android.oat.mk
@@ -112,7 +112,7 @@
 $$(core_image_name): PRIVATE_CORE_IMG_NAME := $$(core_image_name)
 $$(core_image_name): PRIVATE_CORE_OAT_NAME := $$(core_oat_name)
 $$(core_image_name): $$(HOST_CORE_DEX_LOCATIONS) $$(core_dex2oat_dependency)
-	@echo "host dex2oat: $$@ ($$?)"
+	@echo "host dex2oat: $$@"
 	@mkdir -p $$(dir $$@)
 	$$(hide) $(4) $$(DEX2OAT)$(5) --runtime-arg -Xms$(DEX2OAT_IMAGE_XMS) \
 	  --runtime-arg -Xmx$(DEX2OAT_IMAGE_XMX) \
@@ -238,7 +238,7 @@
 $$(core_image_name): PRIVATE_CORE_IMG_NAME := $$(core_image_name)
 $$(core_image_name): PRIVATE_CORE_OAT_NAME := $$(core_oat_name)
 $$(core_image_name): $$(TARGET_CORE_DEX_FILES) $$(core_dex2oat_dependency)
-	@echo "target dex2oat: $$@ ($$?)"
+	@echo "target dex2oat: $$@"
 	@mkdir -p $$(dir $$@)
 	$$(hide) $(4) $$(DEX2OAT)$(5) --runtime-arg -Xms$(DEX2OAT_IMAGE_XMS) \
 	  --runtime-arg -Xmx$(DEX2OAT_IMAGE_XMX) \