Fix portable build on build server by removing depenency on ANDROID_HOST_OUT

Change-Id: I713a156468d14e07c784013c3c37a18c3c075a71
diff --git a/src/image_test.cc b/src/image_test.cc
index dc16a6c..e4deda3 100644
--- a/src/image_test.cc
+++ b/src/image_test.cc
@@ -57,7 +57,7 @@
         mirror::Class* klass = class_linker_->FindSystemClass(descriptor);
         EXPECT_TRUE(klass != NULL) << descriptor;
       }
-      bool success_elf = compiler_driver_->WriteElf(NULL,
+      bool success_elf = compiler_driver_->WriteElf(GetTestAndroidRoot(),
                                                     !kIsTargetBuild,
                                                     dex_files,
                                                     oat_contents,