Fix portable build on build server by removing depenency on ANDROID_HOST_OUT

Change-Id: I713a156468d14e07c784013c3c37a18c3c075a71
diff --git a/src/oat_test.cc b/src/oat_test.cc
index ace52f4..c4bd60e 100644
--- a/src/oat_test.cc
+++ b/src/oat_test.cc
@@ -90,7 +90,7 @@
                                        "lue.art",
                                        *compiler_driver_.get());
   ASSERT_TRUE(success_oat);
-  bool success_elf = compiler_driver_->WriteElf(NULL,
+  bool success_elf = compiler_driver_->WriteElf(GetTestAndroidRoot(),
                                                 !kIsTargetBuild,
                                                 class_linker->GetBootClassPath(),
                                                 oat_contents,