feat(cli): Create a stand-alone launcher for functional tests

The `main` function from Kotest's launcher [1] supports several options,
see [2]. After running `./gradlew :cli-test-launcher:installDist`, use
e.g.

```
./cli-test-launcher/build/install/ort-test-launcher/bin/ort-test-launcher
    --package org.ossreviewtoolkit.plugins.packagemanagers
```

to run all package manager tests.

Resolves #10025.

[1]: https://github.com/kotest/kotest/blob/v5.9.1/kotest-framework/kotest-framework-engine/src/jvmMain/kotlin/io/kotest/engine/launcher/main.kt
[2]: https://github.com/kotest/kotest/blob/v5.9.1/kotest-framework/kotest-framework-engine/src/jvmMain/kotlin/io/kotest/engine/launcher/parseLauncherArgs.kt

Signed-off-by: Sebastian Schuberth <[email protected]>

Author: sschuberth

buildSrc/src/main/kotlin/ort-kotlin-conventions.gradle.kts

@@ -104,6 +104,12 @@ detekt {
 }
 
 java {
+    // Register functional tests as a feature of the main library, see
+    // https://docs.gradle.org/current/userguide/how_to_create_feature_variants_of_a_library.html.
+    registerFeature("funTest") {
+        usingSourceSet(sourceSets["funTest"])
+    }
+
     toolchain {
         // Note that Gradle currently matches the Java language version exactly and does not consider (backward)
         // compatibility between versions, see https://github.com/gradle/gradle/issues/16256.

cli-test-launcher/build.gradle.kts

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2025 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+plugins {
+    // Apply precompiled plugins.
+    id("ort-application-conventions")
+}
+
+application {
+    applicationName = "ort-test-launcher"
+    mainClass = "io.kotest.engine.launcher.MainKt"
+}
+
+val Project.hasFunTests
+    // Do not dig into sourceSets to avoid coupling between projects.
+    get() = projectDir.resolve("src/funTest").isDirectory
+
+dependencies {
+    rootProject.subprojects.filter { it.hasFunTests }.forEach {
+        implementation(project(it.path)) {
+            capabilities {
+                // Note that this uses kebab-case although "registerFeature()" uses camelCase, see
+                // https://github.com/gradle/gradle/issues/31362.
+                @Suppress("UnstableApiUsage")
+                requireFeature("fun-test")
+            }
+        }
+    }
+}
+
+tasks.named<Sync>("installDist") {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+}

settings.gradle.kts

@@ -27,6 +27,7 @@ include(":advisor")
 include(":analyzer")
 include(":cli")
 include(":cli-helper")
+include(":cli-test-launcher")
 include(":clients:bazel-module-registry")
 include(":clients:clearly-defined")
 include(":clients:dos")