Update R8 on DEX test to use system runtime.

Change-Id: Ic855014b3623da0fbc98589043b0a0420e3876a8
diff --git a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/r8ondex/R8CompiledThroughDexTest.java b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/r8ondex/R8CompiledThroughDexTest.java
index 44eb8fa..1e56f81 100644
--- a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/r8ondex/R8CompiledThroughDexTest.java
+++ b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/r8ondex/R8CompiledThroughDexTest.java
@@ -220,7 +220,7 @@
     long start = System.nanoTime();
     ProcessResult javaProcessResult =
         ToolHelper.runJava(
-            TestRuntime.getCheckedInJdk9(),
+            TestRuntime.getSystemRuntime(),
             Collections.singletonList(r8jar),
             ImmutableList.builder()
                 .add("-Xmx1g")