Add proper flags if arch is PowerPC.
We are using now this patch: https://github.com/cms-sw/cmsdist/blob/8bed18da665483f6591cc19ca62e0bd7c1c8f6d7/vecgeom-add-ppc64-cmake-fix.patch which is serving that purpose.
We are using now this patch: https://github.com/cms-sw/cmsdist/blob/8bed18da665483f6591cc19ca62e0bd7c1c8f6d7/vecgeom-add-ppc64-cmake-fix.patch which is serving that purpose.