Better API for creating immutable Skylark lists.

--
MOS_MIGRATED_REVID=132226460
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/CommandHelper.java b/src/main/java/com/google/devtools/build/lib/analysis/CommandHelper.java
index ecf25bd..1890486 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/CommandHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/CommandHelper.java
@@ -28,18 +28,15 @@
 import com.google.devtools.build.lib.rules.AliasProvider;
 import com.google.devtools.build.lib.syntax.SkylarkDict;
 import com.google.devtools.build.lib.syntax.SkylarkList;
-import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.util.OS;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.lib.vfs.PathFragment;
-
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
-
 import javax.annotation.Nullable;
 
 /**
@@ -140,7 +137,7 @@
       }
     }
 
-    this.resolvedTools = new MutableList<>(resolvedToolsBuilder.build());
+    this.resolvedTools = SkylarkList.createImmutable(resolvedToolsBuilder.build());
     this.remoteRunfileManifestMap = SkylarkDict.copyOf(null, remoteRunfileManifestBuilder.build());
     ImmutableMap.Builder<Label, ImmutableCollection<Artifact>> labelMapBuilder =
         ImmutableMap.builder();