[clang] [NFC][analyzer] Remove StmtNodeBuilder (PR #181431)

[Balázs Benics via cfe-commits]

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@@ -267,8 +260,9 @@ class NodeBuilder {
   NodeBuilder(const ExplodedNodeSet &SrcSet, ExplodedNodeSet &DstSet,
               const NodeBuilderContext &Ctx)
       : C(Ctx), Frontier(DstSet) {
-    Frontier.insert(SrcSet);
-    assert(hasNoSinksInFrontier());
+    for (ExplodedNode *Node : SrcSet)
+      if (!Node->isSink())
+        Frontier.insert(Node);
   }
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steakhal wrote:

Is it really the same?
What if the `DstSet` already has elements?

https://github.com/llvm/llvm-project/pull/181431