Update run-test script to pass --Xjitthreshold:0 for jvmti tests

To provide better test coverage for jvmti + jit, lower the
jit threshold to 0 so we jit on the first use of the function.

Test: art/testrunner.py
Change-Id: Ida0edfccd3ae3f4990f6e863f1db00c0a210803b
diff --git a/test/etc/run-test-jar b/test/etc/run-test-jar
index 9d7dc7e..cc22e6e 100755
--- a/test/etc/run-test-jar
+++ b/test/etc/run-test-jar
@@ -644,6 +644,12 @@
     # We used to add flags here that made the runtime debuggable but that is not
     # needed anymore since the plugin can do it for us now.
     FLAGS="${FLAGS} -Xplugin:${plugin}"
+
+    # For jvmti tests, set the threshold of compilation to 0, so we jit on the first
+    # use to provide better test coverage for jvmti + jit. This means we won't run
+    # the default --jit configuration but it is not too important test scenario for
+    # jvmti tests. This is art specific flag, so don't use it with jvm.
+    FLAGS="${FLAGS} -Xjitthreshold:0"
   fi
 fi