Kapt: Fix NPE on JDK 10-11 (KT-26203)

Gradle worker throws NPE when the parameter to the runnable is null.
This patch works that around by passing URL spec as String instead of
File?

libraries/tools/kotlin-gradle-plugin-integration-tests/build.gradle.kts

@@ -125,6 +125,8 @@ tasks.withType<Test> {
 
     systemProperty("kotlinVersion", rootProject.extra["kotlinVersion"] as String)
     systemProperty("runnerGradleVersion", gradle.gradleVersion)
+    systemProperty("jdk10Home", rootProject.extra["JDK_10"] as String)
+    systemProperty("jdk11Home", rootProject.extra["JDK_11"] as String)
 
     val mavenLocalRepo = System.getProperty("maven.repo.local")
     if (mavenLocalRepo != null) {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.gradle
 import org.jetbrains.kotlin.gradle.tasks.USING_JVM_INCREMENTAL_COMPILATION_MESSAGE
 import org.jetbrains.kotlin.gradle.util.*
 import org.junit.Assert
+import org.junit.Assume
 import org.junit.Test
 import java.io.File
 import java.util.zip.ZipFile
@@ -67,6 +68,30 @@ class Kapt3WorkersIT : Kapt3IT() {
             assertSuccessful()
         }
     }
+
+    private fun testSimpleWithCustomJdk(gradleVersion: String, javaHome: File, jdkDescription: String) {
+        val gradleVersionRequired = GradleVersionRequired.AtLeast(gradleVersion)
+
+        Assume.assumeTrue("$jdkDescription isn't available", javaHome.isDirectory)
+        val options = defaultBuildOptions().copy(javaHome = javaHome)
+
+        val project =
+            Project("simple", directoryPrefix = "kapt2", gradleVersionRequirement = gradleVersionRequired)
+        project.build("build", options = options) {
+            assertSuccessful()
+            assertKaptSuccessful()
+        }
+    }
+
+    @Test
+    fun testSimpleWithJdk10() {
+        testSimpleWithCustomJdk("4.7", File(System.getProperty("jdk10Home")!!), "JDK 10")
+    }
+
+    @Test
+    fun testSimpleWithJdk11() {
+        testSimpleWithCustomJdk("5.0", File(System.getProperty("jdk11Home")!!), "JDK 11")
+    }
 }
 
 open class Kapt3IT : Kapt3BaseIT() {