Add conventions only if they are still available

So Gradle could drop conventions in Gradle 8.0 release.

^KT-47047 Fixed

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

@@ -23,7 +23,18 @@ import org.gradle.api.plugins.ExtensionAware
 
 @Deprecated("Conventions are deprecated in Gradle")
 internal inline fun <reified T : Any> Any.addConvention(name: String, plugin: T) {
-    (this as HasConvention).convention.plugins[name] = plugin
+    // Verifying conventions are still available via reflection,
+    // so Gradle could remove them in Gradle 8.0 release
+    val conventionsIsAvailable = try {
+        Class.forName("org.gradle.api.internal.HasConvention")
+        true
+    } catch (_: ClassNotFoundException) {
+        false
+    }
+
+    if (conventionsIsAvailable) {
+        (this as HasConvention).convention.plugins[name] = plugin
+    }
 }
 
 internal inline fun <reified T : Any> Any.addExtension(name: String, extension: T) =