Enable Gradle configuration cache (#1646)

Enable the configuration cache feature in Gradle, and adjust various
pieces of build logic that aren't configuration cache compatible.

pkl-gradle/pkl-gradle.gradle.kts

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+import org.gradle.api.file.ArchiveOperations
+import org.gradle.kotlin.dsl.support.serviceOf
+
 plugins {
   id("pklAllProjects")
   id("pklJavaLibrary")
@@ -80,13 +83,14 @@ val externalReaderJar by
     archiveVersion = ""
 
     // Package all dependencies into the jar (shadow plugin lite).
+    val archiveOps = serviceOf<ArchiveOperations>()
     from(
       externalReader.runtimeClasspath.elements.map { locations ->
         locations.mapNotNull { location ->
           val f = location.asFile
           when {
             f.isDirectory -> f
-            f.isFile -> zipTree(f)
+            f.isFile -> archiveOps.zipTree(f)
             else -> null
           }
         }
@@ -96,18 +100,32 @@ val externalReaderJar by
     manifest { attributes("Main-Class" to "org.pkl.gradle.test.extreader.Main") }
   }
 
-tasks.test {
+// Named class avoids the anonymous inner-class `this$0` field that Gradle's configuration
+// cache cannot serialize when a SAM lambda is created inside a lambda-with-receiver.
+class ExternalReaderArgProvider(
+  private val jarFile: Provider<RegularFile>,
+  private val javaExecutable: Provider<String>,
+) : CommandLineArgumentProvider {
+  override fun asArguments() =
+    listOf(
+      "-DpklGradle.externalReaderJar=${jarFile.get().asFile.absolutePath}",
+      "-DpklGradle.javaExecutable=${javaExecutable.get()}",
+    )
+}
+
+val externalReaderJarFile = externalReaderJar.flatMap { it.archiveFile }
+
+val javaExecutablePath =
+  javaToolchains.launcherFor(java.toolchain).map { it.executablePath.asFile.absolutePath }
+
+// Apply to all Test tasks (not just `test`) so that testJdk* tasks also receive the
+// external-reader system properties without relying on jvmArgumentProviders being copied
+// across tasks (which breaks the configuration cache via stale task references).
+tasks.withType<Test>().configureEach {
   dependsOn(externalReaderJar)
   // Currently the only way to inject system properties from lazy values in Gradle
   // is via `jvmArgumentProviders`.
-  jvmArgumentProviders += CommandLineArgumentProvider {
-    listOf(
-      "-DpklGradle.externalReaderJar=" +
-        externalReaderJar.get().archiveFile.get().asFile.absolutePath,
-      "-DpklGradle.javaExecutable=" +
-        javaToolchains.launcherFor(java.toolchain).get().executablePath.asFile.absolutePath,
-    )
-  }
+  jvmArgumentProviders += ExternalReaderArgProvider(externalReaderJarFile, javaExecutablePath)
 }
 
 publishing {