RFR: JDK-8276837: [macos]: Error when signing the additional launcher

[Andy Herrick]

On Wed, 1 Dec 2021 14:25:52 GMT, Andy Herrick <herrick at openjdk.org> wrote:

> Before signing, unsign all executables and libraries (not just those in runtime).
> Also, run individual file sign and unsign commands in quiet mode.
> Also, add test case to SigningAppImageTest to test that signing app that has additional launcher works, and results in validly signed launcher and additional launcher (original reported problem).

last push was meant to be only one file - but got lots of unrelated changes.
will close this one and open new PR.

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PR: https://git.openjdk.java.net/jdk/pull/6636