ART: disable test 712 for interpreter+gcstress

Temporary suspension of 712-varhandle-invocations for test configs
with interpreter and gcstress .

Bug: 111630237
Test: art/test.py --host --64 --gcstress --interpreter -r -t 712
Change-Id: Ie3111bfb130652f3ae9ae9c2760ecc3d157a33b5
diff --git a/test/knownfailures.json b/test/knownfailures.json
index d4e4ad4..d345d0f 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1022,6 +1022,12 @@
         "description" : ["Test seems to timeout when run with gcstress due to slower unwinding by libbacktrace"]
     },
     {
+        "tests": ["712-varhandle-invocations"],
+        "variant": "interpreter & gcstress",
+        "bug": "b/111630237",
+        "description": ["Test timing out under gcstress possibly due to slower unwinding by libbacktrace"]
+    },
+    {
         "tests": ["712-varhandle-invocations", "624-checker-stringops"],
         "variant": "optimizing & gcstress | speed-profile & gcstress",
         "bug": "b/111545159",