test: Blacklist 987-stack-trace-dumping for javac/dx

Very many tests are currently failing because they import libcore code
which isn't on the standard javac classpath. This new test is one of
those.

A future commit will properly fix this type of failure for all javac/dx
tests, until then simply blacklist it.

Bug: 37636792
Change-Id: Id727372c10ec3ea3ff5913ea8e74c209d3dee575
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 6d207766..3fdd9b3 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -659,9 +659,10 @@
             "969-iface-super",
             "981-dedup-original-dex",
             "984-obsolete-invoke",
-            "985-re-obsolete"
+            "985-re-obsolete",
+            "987-stack-trace-dumping"
         ],
-        "description": "Tests that use javac/dx to build (not jack).",
+        "description": "The tests above fail with --build-with-javac-dx.",
         "env_vars": {"ANDROID_COMPILE_WITH_JACK": "false"},
         "bug": "b/37636792"
     },