Fix make install on archer.
Fix make install on archer.

This fixes make bin/burgers_equation which is a prerequisite for make
install.

iakovos-panourgias/fluidity,jrper/fluidity,jrper/fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,jjo31/ATHAM-Fluidity,jjo31/ATHAM-Fluidity