RFR: JDK-8237607: [macos] Signing app bundle with jpackage fails if runtime is already signed

[Alexander Matveev]

Please review the jpackage fix for bug [1] at [2].

- Fixed by forcing signing even if runtime already signed.
- Original implementation was not taken in consideration that runtime 
can be signed (JDK itself is signed from which jpackage is used or 
runtime provided via --runtime-image).
- Signature of binaries files in runtime will not be change, with this 
fix we will generate new _CodeSignature/CodeResources file which 
contains signatures of all files inside runtime folder signed with user 
provided certificate.

[1] https://bugs.openjdk.java.net/browse/JDK-8237607

[2] http://cr.openjdk.java.net/~almatvee/8237607/webrev.00/

Thanks,
Alexander