cmTarget: Add GetLinkImplMap method.

This is a temporary refactoring artifact.

Source/cmTarget.cxx

@@ -3574,10 +3574,7 @@ cmTarget::GetLinkImplementation(const std::string& config) const
     return 0;
     }
 
-  // Populate the link implementation for this configuration.
+  cmOptionalLinkImplementation& impl = this->GetLinkImplMap(config);
-  std::string CONFIG = cmSystemTools::UpperCase(config);
-  cmOptionalLinkImplementation&
-    impl = this->Internal->LinkImplMap[CONFIG][this];
   if(!impl.LibrariesDone)
     {
     impl.LibrariesDone = true;
@@ -3591,6 +3588,14 @@ cmTarget::GetLinkImplementation(const std::string& config) const
   return &impl;
 }
 
+cmOptionalLinkImplementation&
+cmTarget::GetLinkImplMap(std::string const& config) const
+{
+  // Populate the link implementation for this configuration.
+  std::string CONFIG = cmSystemTools::UpperCase(config);
+  return Internal->LinkImplMap[CONFIG][this];
+}
+
 //----------------------------------------------------------------------------
 cmLinkImplementationLibraries const*
 cmTarget::GetLinkImplementationLibraries(const std::string& config) const

Source/cmTarget.h

@@ -244,6 +244,9 @@ public:
                                           cmOptionalLinkImplementation& impl
                                           ) const;
 
+  cmOptionalLinkImplementation&
+  GetLinkImplMap(std::string const& config) const;
+
   cmTarget const* FindTargetToLink(std::string const& name) const;
 
   /** Strip off leading and trailing whitespace from an item named in