[Fir2IR] Don't compute overriddenSymbols if ir builder is enabled

Ir builder would recompute them anyway, while computation
can lead to triggering computations in lazy classes too early,
which is incorrect.

^KT-65116

compiler/testData/codegen/box/fakeOverride/kt65116.kt

@@ -0,0 +1,24 @@
+// TARGET_BACKEND: JVM_IR
+
+// FILE: Java1.java
+public interface Java1 extends KotlinInterface { }
+
+//FILE: Java2.java
+public interface Java2 {
+    public void bar(int o);
+}
+
+//FILE: 1.kt
+class A: Java1 {
+    override fun bar(o: Int) { }
+}
+
+abstract class B : Java1
+
+interface KotlinInterface : Java2
+
+fun test(b: B) {
+    val k = b.bar(1)
+}
+
+fun box() = "OK"