Add lib suffix to lib directory
Add lib suffix to lib directory

Some systems use e.g. lib64 instead of just lib. On some of those systems though, the LIB_SUFFIX variable doesn't exist, so if it doesn't we assume the empty string.

Thanks to mariolpantunes for the basis of this patch.

Fixes #562.

ROBO3D/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine,ROBO3D/CuraEngine,alephobjects/CuraEngine