Allow for system libraries

[corbett5]

When a host config directly defines the path to a tpl we should use that installation instead of building our own and also use that installation for any dependencies of that tpl. For example when using a system version of hdf5 we shouldn't build hdf5 and then we also need to build axom and conduit against that system version.

[sheltongeosx]

Greatly, completely agree!
Currently I have to figure out how to modify CMakeLists file so that to use my system libraries such as hypre, scotch etc. to build PETSC.
(Sorry, I mean to put this comment to issue #58)

[corbett5]

If you make those changes, could you put them up in a PR? That would be great to have. The way I see it would be some combination of the logic in the main cmake file here and SetupGeosxThirdParty.cmake in the main repo.

[TotoGaz]

Hi @corbett5 @sheltongeosx!
I'm willing to make a suggestion on how we could solve this kind of problems.
Probably I'll start little (with a not so crucial nor so big dependency so I can receive comments from the community).
If it's OK then we see how we scale up on the problem.

[rrsettgast]

We should always put changes that fixed a problem you were having up in PR. That way we can collectively figure out how to address the issue in a general sense.

[TotoGaz]

Do we really want to address this in a close (?) future?
Current directions do not aim this, so I would close the issue for the moment.
It hasn't moved for ages and this will not change.