Add keygen startScripts dependency for distZip and distTar; update scripts path (#855)

Adds missing task dependency to make sure that keygen artifacts (of the
`startScripts` task) are available when core zip is being built.

As a drive-by update the path to the artifacts to use the `outputs`
property of a task, rather than hardcoded folder name.

Author: LukasGasior1

core/build.gradle

@@ -379,6 +379,14 @@ task deb4docker(dependsOn: buildDeb) {
     }
 }
 
-applicationDistribution.from(new File(project(':keygen').buildDir, "scripts")) {
+// This adds the `startScripts` task artifacts from the keygen subproject (i.e. app
+// run scripts: `keygen` and `keygen.bat`) to the "bin" folder in core's distribution.
+// Note that we don't need to manually add keygen jars (to "libs") - this is taken care of
+// by regular dependency management.
+applicationDistribution.from(project(":keygen").getTasksByName("startScripts", false).outputs) {
     into "bin"
 }
+
+// This ensures that keygen scripts are built (and can be copied over to "bin", see above)
+// before we assemble core's packages.
+[distZip, distTar]*.mustRunAfter ":keygen:startScripts"