Mark Boost_DIR as advanced in cmake
Mark Boost_DIR as advanced in cmake

Boost_DIR shows up as NOTFOUND at the top of cmake, even though boost is found.
This isn't a problem, just looks like a problem when running cmake. FindBoost
just doesn't set the value, but does set all the other important values
(Boost_INCLUDE_DIR, etc). So, this change just marks it as advanced, so you
don't see it.

simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim