Code cleanup to avoid LLVM dependency when building with quick only.

Change-Id: I0985c227d775c72fd23975d4c9bf673ba32615c2
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index 7f88471..dab419f 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -287,9 +287,7 @@
                                                         dump_passes,
                                                         &compiler_phases_timings));
 
-    if (compiler_backend_ == CompilerBackend::kPortable) {
-      driver->SetBitcodeFileName(bitcode_filename);
-    }
+    driver->GetCompilerBackend()->SetBitcodeFileName(bitcode_filename);
 
     driver->CompileAll(class_loader, dex_files, timings);