cmGeneratorTarget: Port GetLinkInterfaceLibraries away from cmTarget.

Source/cmGeneratorExpressionNode.cxx

@@ -1109,8 +1109,11 @@ static const struct TargetPropertyNode : public cmGeneratorExpressionNode
 
     if(isInterfaceProperty)
       {
+      cmGeneratorTarget* gHeadTarget =
+          context->Makefile->GetGlobalGenerator()
+          ->GetGeneratorTarget(headTarget);
       if(cmLinkInterfaceLibraries const* iface =
-         gtgt->GetLinkInterfaceLibraries(context->Config, headTarget, true))
+         gtgt->GetLinkInterfaceLibraries(context->Config, gHeadTarget, true))
         {
         linkedTargetsContent =
           getLinkedTargetsContent(iface->Libraries, target,

Source/cmGeneratorTarget.cxx

@@ -2058,7 +2058,7 @@ void processILibs(const std::string& config,
     tgts.push_back(item.Target);
     cmGeneratorTarget* gt = gg->GetGeneratorTarget(item.Target);
     if(cmLinkInterfaceLibraries const* iface =
-       gt->GetLinkInterfaceLibraries(config, headTarget->Target, true))
+       gt->GetLinkInterfaceLibraries(config, headTarget, true))
       {
       for(std::vector<cmLinkItem>::const_iterator
             it = iface->Libraries.begin();
@@ -4592,13 +4592,13 @@ void cmGeneratorTarget::ComputeLinkInterface(const std::string& config,
 //----------------------------------------------------------------------------
 const cmLinkInterfaceLibraries *
 cmGeneratorTarget::GetLinkInterfaceLibraries(const std::string& config,
-                                    cmTarget const* head,
+                                    cmGeneratorTarget const* head,
                                     bool usage_requirements_only) const
 {
   // Imported targets have their own link interface.
   if(this->IsImported())
     {
-    return this->GetImportLinkInterface(config, head,
+    return this->GetImportLinkInterface(config, head->Target,
                                                 usage_requirements_only);
     }
 
@@ -4624,12 +4624,12 @@ cmGeneratorTarget::GetLinkInterfaceLibraries(const std::string& config,
     return &hm.begin()->second;
     }
 
-  cmOptionalLinkInterface& iface = hm[head];
+  cmOptionalLinkInterface& iface = hm[head->Target];
   if(!iface.LibrariesDone)
     {
     iface.LibrariesDone = true;
     this->ComputeLinkInterfaceLibraries(
-      config, iface, head, usage_requirements_only);
+      config, iface, head->Target, usage_requirements_only);
     }
 
   return iface.Exists? &iface : 0;

Source/cmGeneratorTarget.h

@@ -116,7 +116,7 @@ public:
 
   cmLinkInterfaceLibraries const*
     GetLinkInterfaceLibraries(const std::string& config,
-                              cmTarget const* headTarget,
+                              const cmGeneratorTarget* headTarget,
                               bool usage_requirements_only) const;
 
   void ComputeLinkInterfaceLibraries(const std::string& config,