Allow custom package file names

[ScottPierce]

The default packaged dmg is something along the lines of "$appName-$appVersion.dmg". The non-static app version being appended to the base file name, makes it more difficult to add tooling around it in CI. It'd be nice to be able to be able to reference a static file name.

As it is now, my work around is

afterEvaluate {
    // Creates a statically named copy of the dmg
    tasks["packageDmg"].doLast {
        copy {
            from("$buildDir/compose/binaries/main/dmg/$appName-$versionString.dmg")
            into("$buildDir/compose/binaries/main/dmg/")
            rename { "$appName.dmg" }
        }
    }
}

[okushnikov]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.