Try exactly as it says in the docs

mpi_info/Makefile

 mpi_info: mpi_info.c
-	mpicc -o $@ $<
+	mpicc $< -lcudart -o $@

mpi_info/load_modules.sh

 #!/bin/bash
 
 module purge
-module load spack git gcc/7.3.0 openmpi/3.1.4-pmi-cuda-ucx
+module load spack git gcc/7.3.0 cuda/10.1 openmpi/3.1.4-pmi-cuda-ucx
 

mpi_info/mpi_info.c

 #include "mpi.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <cuda_runtime.h>
 
 int main(int argc, char *argv[]) {
     char* local_rank_str = NULL;