[KPM] Implement preliminary 'ExternalVariantApi'

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/external/ExternalVariantApi.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.plugin.mpp.external
+
+import org.gradle.api.Project
+import org.jetbrains.kotlin.gradle.dsl.KotlinTopLevelExtension
+import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.*
+
+@RequiresOptIn("API is intended to build external Kotlin Targets.")
+annotation class ExternalVariantApi
+
+@ExternalVariantApi
+val KotlinTopLevelExtension.project: Project
+    get() = this.project
+
+@ExternalVariantApi
+fun KotlinGradleModule.createExternalJvmVariant(
+    name: String,
+    config: KotlinJvmVariantConfig
+): KotlinJvmVariant {
+    val variant = KotlinJvmVariantFactory(this, config).create(name)
+    fragments.add(variant)
+    return variant
+}
+
+@ExternalVariantApi
+val KotlinGradleVariantInternal.compilationData get() = this.compilationData