Depend on dx binary directly

I5f265132690ad28b3139954fea44eb0c4a43393a changed $(DX) to be a java
command line that runs java -jar dx.jar.  The rest of the test runner
is going executing $(HOST_OUT_EXECUTABLES)/dx directly, so make it
depend on $(HOST_OUT_EXECUTABLES)/dx instead of $(DX).

Test: art/test/testrunner/run_build_test_target.py -j110 art-jit-gcstress
Change-Id: I520e2aae899e4be9c41822c8b2c74468f153d6f9
diff --git a/test/Android.run-test.mk b/test/Android.run-test.mk
index afd9144..6017d28 100644
--- a/test/Android.run-test.mk
+++ b/test/Android.run-test.mk
@@ -19,7 +19,7 @@
 
 # Dependencies for actually running a run-test.
 TEST_ART_RUN_TEST_DEPENDENCIES := \
-  $(DX) \
+  $(HOST_OUT_EXECUTABLES)/dx \
   $(HOST_OUT_EXECUTABLES)/jasmin \
   $(HOST_OUT_EXECUTABLES)/smali \
   $(HOST_OUT_EXECUTABLES)/dexmerger \