sw:vec_iree: Add lit runner feature to facilitate XFAIL filtering

Add runner feature so we can selectivily fail a lit test.

Change-Id: I6ae5d26eed210bdee808a135c2011f68bcf6c7a2

samples/lit.cfg.py

diff --git a/samples/lit.cfg.py b/samples/lit.cfg.py
index b395075..a0bd656 100644
--- a/samples/lit.cfg.py
+++ b/samples/lit.cfg.py
@@ -54,5 +54,7 @@
 
 if runner and runner == "qemu":
     config.environment["TEST_RUNNER_CMD"] = qemu_cmd
+    config.available_features.add("qemu")
 else:
     config.environment["TEST_RUNNER_CMD"] = renode_cmd
+    config.available_features.add("renode")