Do not explicitly link against tinyxml and yaml-cpp for OpenColorIO
support. It is not necessary, since OpenColorIO does not export any symbols of
either of those libraries. Instead, it is risky, if OpenColorIO is NOT built
with tinyxml support or linked against a custom libyaml-cpp, which may not be
the one, blender's cmake checks finds first.

It is up to the environment in those cases to provide correct flags, but
should not be done by blender.