Could not find a suitable mpi compiler (mpicxx or mpic++) whlie using "$ make -f Makefile.shlib auto "

As figure shows, I'm using Linux to install LIGGGHTS, when i type "make -f Makefile.shlib auto", it shows me [auto] Error 2, i tried to set USE_MPI to "OFF", but it did't work, my Question is, how do i using the MPICXX_USR variable? Thanks for your felp.