Get manifest attributes from existing jar task definition

[bluecontainer]

When a gradle project has configuration like this:

jar {
    manifest {
        attributes(
            "Implementation-Title": "Some Application",
            "Implementation-Version": archiveVersion,
            "Main-Class": application.mainClass,
            'Built-By'       : System.properties['user.name'],
            'Build-Timestamp': new java.text.SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ").format(new Date()),
			'Build-Revision' : "${versionDetails().branchName}-${versionDetails().gitHashFull}",
            'Created-By'     : "Gradle ${gradle.gradleVersion}",
            'Build-Jdk'      : "${System.properties['java.version']} (${System.properties['java.vendor']} ${System.properties['java.vm.version']})",
            'Build-OS'       : "${System.properties['os.name']} ${System.properties['os.arch']} ${System.properties['os.version']}"
        )
    }
	zip64 = true
}

I want the jar produced by the micronaut plugin "runnerJar" task to include the manifest attributes specified.

[CLAassistant]

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[melix]

Thanks for the contribution. Would you mind adding a test for this?