ENH: Do not generate install target unless some INSTALL or INSTALL_* commands have been used. This addresses bug#2827.

Source/cmInstallFilesCommand.cxx

@@ -25,6 +25,11 @@ bool cmInstallFilesCommand
     this->SetError("called with incorrect number of arguments");
     return false;
     }
+
+  // Enable the install target.
+  this->Makefile->GetLocalGenerator()
+    ->GetGlobalGenerator()->EnableInstallTarget();
+
   std::vector<std::string> args;
   this->Makefile->ExpandSourceListArguments(argsIn, args, 2);