fix compile

Solver/frameSolver.cpp

@@ -228,6 +228,7 @@ void frameSolver2d::solve ()
 }
 
 void frameSolver2d::exportFrameData(const char * DISPL, const char * M) {
+#if defined(HAVE_POST)
   {
     std::map<int, std::vector<double> > data;
     for (unsigned int i=0;i<_beams.size(); i++){
@@ -258,7 +259,7 @@ void frameSolver2d::exportFrameData(const char * DISPL, const char * M) {
     pv->getData()->writeMSH(M);
     delete pv;
   }
-
+#endif
 }
 
 void frameSolver2d::computeRotationTags ()