Avoid clobbering shared testcluster JAR files when installing modules (#42879)

Author: mark-vieira

buildSrc/src/main/java/org/elasticsearch/gradle/testclusters/ElasticsearchNode.java

@@ -23,6 +23,7 @@
 import org.elasticsearch.gradle.FileSupplier;
 import org.elasticsearch.gradle.OS;
 import org.elasticsearch.gradle.Version;
+import org.gradle.api.file.DuplicatesStrategy;
 import org.gradle.api.logging.Logger;
 import org.gradle.api.logging.Logging;
 
@@ -398,6 +399,9 @@ private void copyExtraConfigFiles() {
     private void installModules() {
         if (distribution == Distribution.INTEG_TEST) {
             modules.forEach(module -> services.copy(spec -> {
+                // ensure we don't override any existing JARs, since these are hardlinks other clusters might be using those files
+                spec.setDuplicatesStrategy(DuplicatesStrategy.EXCLUDE);
+
                 if (module.getName().toLowerCase().endsWith(".zip")) {
                     spec.from(services.zipTree(module));
                 } else if (module.isDirectory()) {