Clone optimization config in Defaulter

#6565

lib/WebpackOptionsDefaulter.js

@@ -193,6 +193,7 @@ class WebpackOptionsDefaulter extends OptionsDefaulter {
 			options => (isProductionLikeMode(options) ? "warning" : false)
 		);
 
+		this.set("optimization", "call", value => Object.assign({}, value));
 		this.set("optimization.removeAvailableModules", true);
 		this.set("optimization.removeEmptyChunks", true);
 		this.set("optimization.mergeDuplicateChunks", true);

test/cases/chunks/runtime/test.filter.js

@@ -0,0 +1,4 @@
+module.exports = function(config) {
+	// This test can't run in development mode as it depends on the flagIncludedChunks optimization
+	return config.mode !== "development";
+};