Keep track of tree artifact inputs in CustomCommandLine.Builder .

PiperOrigin-RevId: 206203357
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
index 8dab651..9e2ca29 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
@@ -1831,6 +1831,9 @@
           if (allowedFileTypes.apply(sourceArtifact.getFilename())) {
             return;
           }
+          if (sourceArtifact.isTreeArtifact()) {
+            return;
+          }
         }
         attributeError(
             attribute.getName(),