subprojectSourceSets

Kotlin Multiplatform source-set names per subproject, empty for non-KMP modules.

Format: Map<subprojectPath, List<sourceSetName>>, e.g. { ":core:domain" -> ["commonMain", "androidMain", "iosMain"] }.

Populates ModuleNode.sourceSets. Read reflectively from the Kotlin extension by the plugins, so a module whose extension cannot be read simply contributes an empty list.