define TETLIBRARY to avoid exit()

Mesh/meshGRegionBoundaryRecovery.cpp

@@ -89,6 +89,7 @@ static double orient4d(double*, double *, double *, double *, double *,
                        double, double, double, double, double){ return 0.; }
 static int clock(){ return 0; }
 #define clock_t int
+#define TETLIBRARY
 #include "tetgenBR.h"
 #include "tetgenBR.cxx"