Add some type arguments to make Bazel compile again.

--
MOS_MIGRATED_REVID=131570943
diff --git a/src/test/java/com/google/devtools/build/lib/standalone/StandaloneSpawnStrategyTest.java b/src/test/java/com/google/devtools/build/lib/standalone/StandaloneSpawnStrategyTest.java
index 1a9e478..b53c1ca 100644
--- a/src/test/java/com/google/devtools/build/lib/standalone/StandaloneSpawnStrategyTest.java
+++ b/src/test/java/com/google/devtools/build/lib/standalone/StandaloneSpawnStrategyTest.java
@@ -146,7 +146,7 @@
         new SingleBuildFileCache(execRoot.getPathString(), execRoot.getFileSystem()),
         null,
         outErr,
-        ImmutableMap.of(),
+        ImmutableMap.<String, String>of(),
         null);
   }