External dependencies: throw exception if jdk ouput directory cannot be deleted

build/dependencies/setupJdk.gradle

@@ -56,7 +56,11 @@ task setupJdk18(dependsOn: downloadJdk18) {
 
 def unpackJdk(jdkArchive, outputDir) {
   logger.info("Unpacking $jdkArchive to ${outputDir}")
-  file(outputDir).deleteDir()
+  if (file(outputDir).exists()) {
+    if (!file(outputDir).deleteDir()) {
+      throw new Exception("unpackJdk: Unable to delete folder: $outputDir")
+    }
+  }
   def currentOs = org.gradle.internal.os.OperatingSystem.current()
   if (currentOs.isWindows()) {
     copy {