cmGlobalVisualStudio7Generator: make `SupportsCxxModuleDyndep` protected

The generator target will want to ask this question when determining
whether C++ modules are supported or not.

Source/cmGlobalVisualStudio7Generator.h

@@ -115,6 +115,8 @@ public:
 
   cmIDEFlagTable const* ExtraFlagTable;
 
+  virtual bool SupportsCxxModuleDyndep() const { return false; }
+
 protected:
   cmGlobalVisualStudio7Generator(cmake* cm,
                                  std::string const& platformInGeneratorName);
@@ -158,8 +160,6 @@ protected:
     cmValue typeGuid,
     const std::set<BT<std::pair<std::string, bool>>>& dependencies) = 0;
 
-  virtual bool SupportsCxxModuleDyndep() const { return false; }
-
   std::string ConvertToSolutionPath(const std::string& path);
 
   std::set<std::string> IsPartOfDefaultBuild(