File _multibuild of Package boost171

<multibuild>
  <package>gnu-hpc</package>
  <package>gnu-openmpi2-hpc</package>
  <package>gnu-openmpi3-hpc</package>
  <package>gnu-mvapich2-hpc</package>
  <package>gnu-mpich-hpc</package>
</multibuild>