Do not use $? in recipe

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

Change-Id: Ibc3a18dc5739b5008b156d2672a626621e046f5a
diff --git a/core/dex_preopt_libart_boot.mk b/core/dex_preopt_libart_boot.mk
index afd61eb..253afe2 100644
--- a/core/dex_preopt_libart_boot.mk
+++ b/core/dex_preopt_libart_boot.mk
@@ -48,7 +48,7 @@
 $($(my_2nd_arch_prefix)DEFAULT_DEX_PREOPT_BUILT_IMAGE_FILENAME): PRIVATE_2ND_ARCH_VAR_PREFIX := $(my_2nd_arch_prefix)
 # Use dex2oat debug version for better error reporting
 $($(my_2nd_arch_prefix)DEFAULT_DEX_PREOPT_BUILT_IMAGE_FILENAME) : $(LIBART_TARGET_BOOT_DEX_FILES) $(DEX2OAT_DEPENDENCY)
-	@echo "target dex2oat: $@ ($?)"
+	@echo "target dex2oat: $@"
 	@mkdir -p $(dir $@)
 	@mkdir -p $(dir $($(PRIVATE_2ND_ARCH_VAR_PREFIX)LIBART_TARGET_BOOT_OAT_UNSTRIPPED))
 	$(hide) $(DEX2OAT) --runtime-arg -Xms$(DEX2OAT_IMAGE_XMS) --runtime-arg -Xmx$(DEX2OAT_IMAGE_XMX) \