fix(gradle-default-package-task): Set default packagingJdk for bundle-jre

Author: orange-guo

src/main/java/io/github/fvarrui/javapackager/gradle/DefaultPackageTask.java

@@ -1,10 +1,11 @@
 package io.github.fvarrui.javapackager.gradle;
 
-import static io.github.fvarrui.javapackager.utils.ObjectUtils.defaultIfNull;
-
+import io.github.fvarrui.javapackager.packagers.Context;
 import io.github.fvarrui.javapackager.packagers.Packager;
 import io.github.fvarrui.javapackager.packagers.PackagerFactory;
 
+import static io.github.fvarrui.javapackager.utils.ObjectUtils.defaultIfNull;
+
 /**
  * Default packaging task for Gradle 
  */
@@ -51,7 +52,7 @@ protected Packager createPackager() throws Exception {
 					.organizationName(extension.getOrganizationName())
 					.organizationUrl(extension.getOrganizationUrl())
 					.outputDirectory(extension.getOutputDirectory())
-					.packagingJdk(extension.getPackagingJdk())
+					.packagingJdk(defaultIfNull(extension.getPackagingJdk(), Context.getGradleContext().getDefaultToolchain()))
 					.runnableJar(extension.getRunnableJar())
 					.scripts(extension.getScripts())
 					.useResourcesAsWorkingDir(extension.isUseResourcesAsWorkingDir())