Makes elasticsearch plugin generation depend on cpp (elastic/elasticsearch#433)

The changes the way the Elasticsearch plugin module gets the cpp code when running the bundlePlugin task. Instead of manually going into the cpp builds output and grabbing the folders it depends on the buildZip task of the :cpp project and grabs the resource that task builds. This means that it does not matter if the cpp buildZip task is changed as long as it results in a zip being generated.

Original commit: elastic/x-pack-elasticsearch@257e5df2e7

elasticsearch/build.gradle

@@ -40,14 +40,7 @@ integTest {
 integTest.mustRunAfter noBootstrapTest
 
 bundlePlugin {
-  from("${rootDir}/cppdistribution") {
-    into '.'
-    // Don't copy Windows import libraries
-    exclude "**/*.lib"
-    // Don't copy the test support library
-    exclude "**/libPreTest.*"
-    includeEmptyDirs = false
-  }
+  from { zipTree(project(':cpp').buildZip.outputs.files.singleFile) }
 }
 
-bundlePlugin.dependsOn(':cpp:strip')
+bundlePlugin.dependsOn(':cpp:buildZip')