Fix classpath of bootBuildImage integration tests

Author: wilkinsona

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/testkit/PluginClasspathGradleBuild.java

@@ -80,6 +80,7 @@ private List<File> pluginClasspath() {
 				new File(pathOfJarContaining("org.jetbrains.kotlin.daemon.client.KotlinCompilerClient")),
 				new File(pathOfJarContaining(KotlinCompilerPluginSupportPlugin.class)),
 				new File(pathOfJarContaining(LanguageSettings.class)),
+				new File(pathOfJarContaining("org.apache.commons.lang3.ArrayFill")),
 				new File(pathOfJarContaining("org.apache.commons.io.Charsets")),
 				new File(pathOfJarContaining(ArchiveEntry.class)), new File(pathOfJarContaining(BuildRequest.class)),
 				new File(pathOfJarContaining(HttpClientConnectionManager.class)),