Use Label for equality comparison instead of Target: Target objects don't have equality.

PiperOrigin-RevId: 165039514
diff --git a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
index a9130f7..0121e00 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
@@ -578,7 +578,7 @@
     labelToTarget.put(from.getLabel(), from);
     while (!toVisit.isEmpty()) {
       Target current = toVisit.removeFirst();
-      if (to.equals(current)) {
+      if (to.getLabel().equals(current.getLabel())) {
         List<Label> labelPath = Digraph.getPathToTreeNode(nodeToParent, to.getLabel());
         ImmutableList.Builder<Target> targetPathBuilder = ImmutableList.builder();
         for (Label label : labelPath) {