buildbot: exit 0 at the end of the script

This permits script to return correct state when skipping packaging

util/buildbot/buildwin32.sh

@@ -153,4 +153,5 @@ make -j2
 
 [ "x$NO_PACKAGE" = "x" ] && make package
 
+exit 0
 # EOF

util/buildbot/buildwin64.sh

@@ -154,4 +154,5 @@ make -j2
 
 [ "x$NO_PACKAGE" = "x" ] && make package
 
+exit 0
 # EOF