cmGlobalNinjaGenerator: Save path to 'ninja' tool very early

Keep it in a member variable for convenient reference.  Set the
value as soon as it is known.

Source/cmGlobalNinjaGenerator.cxx

@@ -585,6 +585,15 @@ void cmGlobalNinjaGenerator::Generate()
   this->CloseBuildFileStream();
 }
 
+void cmGlobalNinjaGenerator::FindMakeProgram(cmMakefile* mf)
+{
+  this->cmGlobalGenerator::FindMakeProgram(mf);
+  if (const char* ninjaCommand = mf->GetDefinition("CMAKE_MAKE_PROGRAM"))
+    {
+    this->NinjaCommand = ninjaCommand;
+    }
+}
+
 void cmGlobalNinjaGenerator
 ::EnableLanguage(std::vector<std::string>const& langs,
                  cmMakefile* mf,
@@ -1260,8 +1269,7 @@ std::string cmGlobalNinjaGenerator::ninjaCmd() const
 {
   cmLocalGenerator* lgen = this->LocalGenerators[0];
   if (lgen) {
-    return lgen->ConvertToOutputFormat(
-             lgen->GetMakefile()->GetRequiredDefinition("CMAKE_MAKE_PROGRAM"),
+    return lgen->ConvertToOutputFormat(this->NinjaCommand,
                                        cmLocalGenerator::SHELL);
   }
   return "ninja";

Source/cmGlobalNinjaGenerator.h

@@ -320,7 +320,7 @@ protected:
 
 private:
   virtual std::string GetEditCacheCommand() const;
-
+  virtual void FindMakeProgram(cmMakefile* mf);
 
   void OpenBuildFileStream();
   void CloseBuildFileStream();
@@ -392,6 +392,8 @@ private:
 
   typedef std::map<std::string, cmGeneratorTarget*> TargetAliasMap;
   TargetAliasMap TargetAliases;
+
+  std::string NinjaCommand;
 };
 
 #endif // ! cmGlobalNinjaGenerator_h