Slight tweak to IPO build commands to ensure it works if compiler does not support IPO.
Slight tweak to IPO build commands to ensure it works if compiler does not support IPO.

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