build.gradle

// root build.gradle

static boolean isNewTypeProject(Project project) {
    project.ext.has("isBuildSystemProject")
}

static boolean isAndroidLibraryPlugin(Plugin plugin) {
    plugin.getClass().canonicalName in ["com.android.build.gradle.LibraryPlugin",
                                        "com.android.build.gradle.AppPlugin"]
}

static boolean isJavaLibraryPlugin(Plugin plugin) {
    plugin.getClass().canonicalName in ["org.gradle.api.plugins.JavaPlugin",
                                        "org.gradle.api.plugins.JavaLibraryPlugin"]
}

subprojects { project ->
    if (isNewTypeProject(project)) {  // <-- this check doesn't work !

        println "${project.displayName} has been migrated to new Build System"

    } else {
        // feature module comes here intead
        println "${project.displayName} has NOT been migrated to new Build System"

        project.plugins.whenPluginAdded { plugin ->
            if (isAndroidLibraryPlugin(plugin)) {
                project.apply from: "$rootProject.projectDir/../sdakit/scripts/gradle/android_subproject.gradle"
            }
            if (isJavaLibraryPlugin(plugin)) {
                project.apply from: "$rootProject.projectDir/../sdakit/scripts/gradle/java_subproject.gradle"
            }
        }
    }
}