Run debuggable tests on art-jit

We were not running jit-debuggable tests anywhere. Adding them to the
art-jit column should give us coverage for this configuration.

Test: ./test/testrunner/run_build_test_target.py art-jit
Change-Id: I7df9c017c9237910c4950888f04dd0a45eeac8da
diff --git a/test/knownfailures.json b/test/knownfailures.json
index a202044..aac2840 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -362,6 +362,12 @@
     },
     {
         "test_patterns": ["616-cha.*"],
+        "description": ["cha tests rely on knowing the exact set of optimizations available. ",
+                        "Debuggable runtimes change the set of optimizations."],
+        "variant": "debuggable"
+    },
+    {
+        "test_patterns": ["616-cha.*"],
         "description": ["cha tests rely on knowing more about the state of the JIT then is possible with jvmti-stress"],
         "variant": "jvmti-stress & jit | redefine-stress & jit"
     },