C#: Exclude CIL arguments from ArgumentNode when they are compiled from source

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowDispatch.qll

@@ -415,6 +415,9 @@ class CilDataFlowCall extends DataFlowCall, TCilCall {
 
   CilDataFlowCall() { this = TCilCall(call) }
 
+  /** Gets the underlying CIL call. */
+  CIL::Call getCilCall() { result = call }
+
   override DataFlowCallable getARuntimeTarget() {
     // There is no dispatch library for CIL, so do not consider overrides for now
     result.getUnderlyingCallable() = getCallableForDataFlow(call.getTarget())

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

@@ -1181,7 +1181,7 @@ private module ArgumentNodes {
     ExplicitArgumentNode() {
       this.asExpr() instanceof Argument
       or
-      this.asExpr() = any(CIL::Call call).getAnArgument()
+      this.asExpr() = any(CilDataFlowCall cc).getCilCall().getAnArgument()
     }
 
     override predicate argumentOf(DataFlowCall call, ArgumentPosition pos) {