Set CMake policy CMP0079 when version >= 3.13
Set CMake policy CMP0079 when version >= 3.13

liangjg/openmc,shikhar413/openmc,smharper/openmc,walshjon/openmc,liangjg/openmc,walshjon/openmc,shikhar413/openmc,paulromano/openmc,liangjg/openmc,mit-crpg/openmc,mit-crpg/openmc,shikhar413/openmc,shikhar413/openmc,amandalund/openmc,paulromano/openmc,mit-crpg/openmc,amandalund/openmc,smharper/openmc,liangjg/openmc,amandalund/openmc,paulromano/openmc,mit-crpg/openmc,amandalund/openmc,paulromano/openmc,smharper/openmc,smharper/openmc,walshjon/openmc,walshjon/openmc