Fix the path for findbugs.

Change-Id: I45485f1aeaf7fc3db2839f42829278d8c0ec97e3
diff --git a/core/Makefile b/core/Makefile
index 68b76ec..9e10417 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1644,11 +1644,11 @@
 INTERNAL_FINDBUGS_HTML_TARGET := $(PRODUCT_OUT)/findbugs.html
 $(INTERNAL_FINDBUGS_XML_TARGET): $(ALL_FINDBUGS_FILES)
 	@echo UnionBugs: $@
-	$(hide) prebuilt/common/findbugs/bin/unionBugs $(ALL_FINDBUGS_FILES) \
+	$(hide) $(FINDBUGS_DIR)/unionBugs $(ALL_FINDBUGS_FILES) \
 	> $@
 $(INTERNAL_FINDBUGS_HTML_TARGET): $(INTERNAL_FINDBUGS_XML_TARGET)
 	@echo ConvertXmlToText: $@
-	$(hide) prebuilt/common/findbugs/bin/convertXmlToText -html:fancy.xsl \
+	$(hide) $(FINDBUGS_DIR)/convertXmlToText -html:fancy.xsl \
 	$(INTERNAL_FINDBUGS_XML_TARGET) > $@
 
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