Genex: Extend EvaluatingLinkLibraries to also check the top target name.

This will allow testing whether we are evaluating the link libraries
of a particular target.

Source/cmGeneratorExpressionDAGChecker.cxx

@@ -139,7 +139,7 @@ cmGeneratorExpressionDAGChecker::checkGraph() const
 }
 
 //----------------------------------------------------------------------------
-bool cmGeneratorExpressionDAGChecker::EvaluatingLinkLibraries()
+bool cmGeneratorExpressionDAGChecker::EvaluatingLinkLibraries(const char *tgt)
 {
   const cmGeneratorExpressionDAGChecker *top = this;
   const cmGeneratorExpressionDAGChecker *parent = this->Parent;
@@ -150,6 +150,12 @@ bool cmGeneratorExpressionDAGChecker::EvaluatingLinkLibraries()
     }
 
   const char *prop = top->Property.c_str();
+
+  if (tgt)
+    {
+    return top->Target == tgt && strcmp(prop, "LINK_LIBRARIES") == 0;
+    }
+
   return (strcmp(prop, "LINK_LIBRARIES") == 0
        || strcmp(prop, "LINK_INTERFACE_LIBRARIES") == 0
        || strcmp(prop, "IMPORTED_LINK_INTERFACE_LIBRARIES") == 0

Source/cmGeneratorExpressionDAGChecker.h

@@ -47,7 +47,7 @@ struct cmGeneratorExpressionDAGChecker
   void reportError(cmGeneratorExpressionContext *context,
                    const std::string &expr);
 
-  bool EvaluatingLinkLibraries();
+  bool EvaluatingLinkLibraries(const char *tgt = 0);
 
 #define DECLARE_TRANSITIVE_PROPERTY_METHOD(METHOD) \
   bool METHOD () const;