Blacklist test under gcstress.

Test: libcore
Change-Id: I01b7297d3dfeefd769fb68cfb8d3e74e75307b7c
diff --git a/tools/libcore_gcstress_failures.txt b/tools/libcore_gcstress_failures.txt
new file mode 100644
index 0000000..e049cb3
--- /dev/null
+++ b/tools/libcore_gcstress_failures.txt
@@ -0,0 +1,13 @@
+/*
+ * This file contains expectations for ART's buildbot when running gcstress.
+ * The script that uses this file is art/tools/run-libcore-tests.sh.
+ */
+
+[
+{
+  description: "Timeouts on target with gcstress.",
+  result: EXEC_FAILED,
+  modes: [device],
+  names: ["libcore.javax.crypto.CipherBasicsTest#testGcmEncryption"]
+}
+]