i would install the github for my mining server , all works okay , after make -f makefile.unix

i get this error :

/usr/bin/ld: cannot find -lgmp
collect2: error: ld returned 1 exit status
makefile.unix:214: recipe for target 'XYLOd' failed
make: *** [XYLOd] Error 1


anyone know , what i can do ?