BuildBoost.cmake (used when we're building the submodule) doesn't
provide parity with FindBoost.cmake (used with system Boost).
Specifically, it doesn't set the _FOUND variables for the various
components, making it hard to depend on finding those features.
Set Boost_<component>_FOUND for all the components we're building in
BuildBoost.cmake to make using these variables possible.
Signed-off-by: Daniel Gryniewicz <dang@redhat.com>
