Enable disabling incremental compilation for tests

compiler/backend/src/org/jetbrains/kotlin/codegen/MultifileClassCodegen.kt

@@ -247,7 +247,7 @@ public class MultifileClassCodegen(
         }
 
         private fun getCompiledPackageFragment(packageFqName: FqName, state: GenerationState): PackageFragmentDescriptor? =
-                if (!IncrementalCompilation.ENABLED) null
+                if (!IncrementalCompilation.isEnabled()) null
                 else state.module.getPackage(packageFqName).fragments.firstOrNull { fragment ->
                     fragment is IncrementalPackageFragmentProvider.IncrementalPackageFragment &&
                     fragment.target == state.targetId

compiler/backend/src/org/jetbrains/kotlin/codegen/PackageCodegen.java

@@ -141,7 +141,7 @@ public class PackageCodegen {
 
     @Nullable
     private PackageFragmentDescriptor getCompiledPackageFragment(@NotNull FqName fqName) {
-        if (!IncrementalCompilation.ENABLED) {
+        if (!IncrementalCompilation.isEnabled()) {
             return null;
         }