This patch readds the missing functionality of running codesign on
certain launchers on macosx. In the old build, it was always run, but
failing if the openjdk_codesign certificate wasn't present on the
system. Make ignored this failure. In this patch, configure tests that
the certificate is there and disables running codesign if it isn't,
reducing pointless error messages in the build log.
http://cr.openjdk.java.net/~erikj/8013489/webrev.01/
/Erik