Fix the usual build hanging issue by using -o (overwrite without prompting) option with unzip

This should fix the common problem when googlelogin-client and google-framework are both included

core/definitions.mk

@@ -1224,7 +1224,7 @@ define unzip-jar-files
       echo Missing file $$f; \
       exit 1; \
     fi; \
-    unzip -q $$f -d $(2); \
+    unzip -qo $$f -d $(2); \
     (cd $(2) && rm -rf META-INF); \
   done
 endef