[Gradle] Register sourcesJar during KotlinSoftwareComponent init

sourcesJar task should be available as soon as kotlin multiplatform
plugin is applied before actual evaluation.

Although copySpec of sourcesJar task will be updated in afterEvaluate
block since user should define themselves targets and intermediate
source sets between them.

^KT-55230

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/KotlinSoftwareComponent.kt

@@ -16,6 +16,8 @@ import org.gradle.api.internal.component.SoftwareComponentInternal
 import org.gradle.api.internal.component.UsageContext
 import org.gradle.api.provider.SetProperty
 import org.gradle.api.publish.maven.MavenPublication
+import org.gradle.api.tasks.TaskProvider
+import org.gradle.jvm.tasks.Jar
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
 import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation.Companion.MAIN_COMPILATION_NAME
@@ -79,10 +81,11 @@ abstract class KotlinSoftwareComponent(
                 }
             }
 
-            configureSourcesJarArtifact()
+            val sourcesElements = metadataTarget.sourcesElementsConfigurationName
+            addSourcesJarArtifactToConfiguration(sourcesElements)
             this += DefaultKotlinUsageContext(
                 compilation = metadataTarget.compilations.getByName(MAIN_COMPILATION_NAME),
-                dependencyConfigurationName = metadataTarget.sourcesElementsConfigurationName,
+                dependencyConfigurationName = sourcesElements,
                 includeIntoProjectStructureMetadata = false,
             )
         }
@@ -92,11 +95,14 @@ abstract class KotlinSoftwareComponent(
         return _usages
     }
 
-    private fun configureSourcesJarArtifact(): PublishArtifact {
-        fun allPublishableCommonSourceSets() = getCommonSourceSetsForMetadataCompilation(project) +
-                getHostSpecificMainSharedSourceSets(project)
+    private fun allPublishableCommonSourceSets() = getCommonSourceSetsForMetadataCompilation(project) +
+            getHostSpecificMainSharedSourceSets(project)
 
-        val sourcesJarTask = sourcesJarTaskNamed(
+    /**
+     * Registration (during object init) of [sourcesJarTask] is required for cases when
+     * user build scripts want to have access to sourcesJar task to configure it
+     */
+    private val sourcesJarTask: TaskProvider<Jar> = sourcesJarTaskNamed(
             "sourcesJar",
             name,
             project,
@@ -104,7 +110,8 @@ abstract class KotlinSoftwareComponent(
             name.toLowerCase()
         )
 
-        return project.artifacts.add(metadataTarget.sourcesElementsConfigurationName, sourcesJarTask) { sourcesJarArtifact ->
+    private fun addSourcesJarArtifactToConfiguration(configurationName: String): PublishArtifact {
+        return project.artifacts.add(configurationName, sourcesJarTask) { sourcesJarArtifact ->
             sourcesJarArtifact.classifier = "sources"
         }
     }