File _multibuild of Package boost.175

<multibuild>
  <package>base</package>
  <package>extra</package>
  <package>gnu-hpc</package>
  <package>gnu-openmpi2-hpc</package>
  <package>gnu-openmpi3-hpc</package>
  <package>gnu-openmpi4-hpc</package>
  <package>gnu-mvapich2-hpc</package>
  <package>gnu-mpich-hpc</package>
</multibuild>