Fix dependency checks on libs when generating Eclipse configuration.

Currently this fails because the Eclipse configuration splits the main and test
folders into separate projects to avoid circular dependencies.

Relates elastic#29336

libs/build.gradle

@@ -34,6 +34,7 @@ subprojects {
                 Project depProject = dependencyToProject(dep)
                 if (depProject != null
                         && false == depProject.path.equals(':libs:elasticsearch-core')
+                        && false == isEclipse 
                         && depProject.path.startsWith(':libs')) {
                     throw new InvalidUserDataException("projects in :libs "
                             + "may not depend on other projects libs except "