Build: Allow deps to be a direct jar (elastic#28096)

Currently the code which disable transitive dependencies assumes all
deps are a "module dependency" in gradle. But a jar file dep is not.
This commit relaxes the closure signature to allow any dependency and
only enforce the transitive disabling for module dependencies.

Author: rjernst

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -32,6 +32,7 @@ import org.gradle.api.Project
 import org.gradle.api.Task
 import org.gradle.api.XmlProvider
 import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.Dependency
 import org.gradle.api.artifacts.ModuleDependency
 import org.gradle.api.artifacts.ModuleVersionIdentifier
 import org.gradle.api.artifacts.ProjectDependency
@@ -274,8 +275,9 @@ class BuildPlugin implements Plugin<Project> {
         })
 
         // force all dependencies added directly to compile/testCompile to be non-transitive, except for ES itself
-        Closure disableTransitiveDeps = { ModuleDependency dep ->
-            if (!(dep instanceof ProjectDependency) && dep.group.startsWith('org.elasticsearch') == false) {
+        Closure disableTransitiveDeps = { Dependency dep ->
+            if (dep instanceof ModuleDependency && !(dep instanceof ProjectDependency)
+                    && dep.group.startsWith('org.elasticsearch') == false) {
                 dep.transitive = false
 
                 // also create a configuration just for this dependency version, so that later