The rpm-ostree-devel package includes the header files for rpm-ostree-libs.
acquired package info from repodata DB: repodata/1b484c8eb5b8229fba6b5a5b11fe895b7104760061a10c49a7af41194c2b52a2-primary.sqlite.bz2
The rpm-ostree-libs package includes the shared library for rpm-ostree.