Ensure that Kotlin implementation of QuarkusApplication works properly

Fixes: #30190

Follows up on: #30058 (which incorrectly checked for QuarkusApplication
as a superclass)

Author: geoand

core/deployment/src/main/java/io/quarkus/deployment/steps/MainClassBuildStep.java

@@ -419,25 +419,15 @@ public MainClassBuildItem mainClassBuildStep(BuildProducer<GeneratedClassBuildIt
     }
 
     private static String sanitizeMainClassName(ClassInfo mainClass, IndexView index) {
-        String className = mainClass.name().toString();
+        DotName mainClassDotName = mainClass.name();
+        String className = mainClassDotName.toString();
         if (isKotlinClass(mainClass)) {
             MethodInfo mainMethod = mainClass.method("main",
                     ArrayType.create(Type.create(DotName.createSimple(String.class.getName()), Type.Kind.CLASS), 1));
             if (mainMethod == null) {
-                ClassInfo classToCheck = mainClass;
-                boolean hasQuarkusApplicationSuperClass = false;
-                while (classToCheck != null) {
-                    DotName superName = classToCheck.superName();
-                    if (superName.equals(QUARKUS_APPLICATION)) {
-                        hasQuarkusApplicationSuperClass = true;
-                        break;
-                    }
-                    if (superName.equals(OBJECT)) {
-                        break;
-                    }
-                    classToCheck = index.getClassByName(superName);
-                }
-                if (!hasQuarkusApplicationSuperClass) {
+                boolean hasQuarkusApplicationInterface = index.getAllKnownImplementors(QUARKUS_APPLICATION).stream().map(
+                        ClassInfo::name).anyMatch(d -> d.equals(mainClassDotName));
+                if (!hasQuarkusApplicationInterface) {
                     className += "Kt";
                 }
             }

integration-tests/gradle/src/main/resources/kotlin-grpc-project/src/main/kotlin/org/acme/Main.kt

@@ -0,0 +1,15 @@
+package org.acme
+
+import io.quarkus.runtime.Quarkus
+import io.quarkus.runtime.QuarkusApplication
+import io.quarkus.runtime.annotations.QuarkusMain
+
+@QuarkusMain
+class Main : QuarkusApplication {
+
+    @Throws(Exception::class)
+    override fun run(vararg args: String?): Int {
+        Quarkus.waitForExit()
+        return 0
+    }
+}