Add test-suite-tag for ART gtests.

This should make it easier to run the tests in eng-prod.

Bug: 152379281
Change-Id: I4a1b5ee903221e74aab2bd52874eb25e2b299a3f
diff --git a/test/gtests-target.xml b/test/gtests-target.xml
index 7152835..62aa938 100644
--- a/test/gtests-target.xml
+++ b/test/gtests-target.xml
@@ -14,6 +14,7 @@
      limitations under the License.
 -->
 <configuration description="ART gtests">
+    <option name="test-suite-tag" value="art" />
     <target_preparer class="com.android.tradefed.targetprep.InstallApexModuleTargetPreparer" >
         <option name="test-file-name" value="com.android.art.testing.apex" />
     </target_preparer>