RFR: 8013489: New build system does not run codesign on SA-related launchers on OS X

[Erik Joelsson]

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