cmGlobalGenerator: Compute export() related classes early.

Simplify CMP0024 handling.

Source/cmGlobalGenerator.cxx

@@ -1199,6 +1199,7 @@ void cmGlobalGenerator::CreateGenerationObjects(TargetTypes targetTypes)
   cmDeleteAll(this->GeneratorTargets);
   this->GeneratorTargets.clear();
   this->CreateGeneratorTargets(targetTypes);
+  this->ComputeBuildFileGenerators();
 }
 
 cmExportBuildFileGenerator*
@@ -1279,8 +1280,6 @@ bool cmGlobalGenerator::Compute()
       this->CreateQtAutoGeneratorsTargets();
 #endif
 
-  this->ComputeBuildFileGenerators();
-
   unsigned int i;
 
   // Add generator specific helper commands

Source/cmGlobalGenerator.h

@@ -365,8 +365,6 @@ public:
   bool GetConfigureDoneCMP0026() const
   { return this->ConfigureDoneCMP0026AndCMP0024; }
 
-  void ComputeBuildFileGenerators();
-
   std::string MakeSilentFlag;
 protected:
   typedef std::vector<cmLocalGenerator*> GeneratorVector;
@@ -471,6 +469,8 @@ private:
   void CheckCompilerIdCompatibility(cmMakefile* mf,
                                     std::string const& lang) const;
 
+  void ComputeBuildFileGenerators();
+
   cmExternalMakefileProjectGenerator* ExtraGenerator;
 
   // track files replaced during a Generate

Source/cmIncludeCommand.cxx

@@ -126,7 +126,6 @@ bool cmIncludeCommand
         }
       }
     gg->CreateGenerationObjects();
-    gg->ComputeBuildFileGenerators();
     gg->GenerateImportFile(fname_abs);
     }