Ensure pluginCompileOnly participates in variant-aware selection

Two variants of KGP are published as of KGP 1.7. Without specifying an
attribute to match on the consuming configuration Gradle will refuse to
match either one. Adding an attribute to match on will make Gradle select
a variant when resolving dependencies for the manually created
pluginCompileOnly configuration.

detekt-gradle-plugin/build.gradle.kts

@@ -70,6 +70,10 @@ val functionalTestImplementation: Configuration by configurations.getting
 
 configurations.compileOnly { extendsFrom(pluginCompileOnly) }
 
+pluginCompileOnly.attributes {
+    attribute(Category.CATEGORY_ATTRIBUTE, objects.named(Category::class.java, "library"))
+}
+
 dependencies {
     compileOnly(libs.kotlin.gradlePluginApi)
     implementation(libs.sarif4k)