Make --jvm work again

A previous commit broke --jvm by making it be passed dex2oat args. Fix
this bug.

Change-Id: I22864ef876c7b3c174af029fe2f1a76cf7825fa7
diff --git a/test/run-test b/test/run-test
index 925d8f2..9b311dd 100755
--- a/test/run-test
+++ b/test/run-test
@@ -151,6 +151,7 @@
     elif [ "x$1" = "x--jvm" ]; then
         target_mode="no"
         runtime="jvm"
+        image_args=""
         prebuild_mode="no"
         NEED_DEX="false"
         USE_JACK="false"