The rpm-ostree-devel package includes the header files for rpm-ostree-libs.
acquired package info from repodata DB: repodata/79ff1068e9d07a15d2712f09bc476abe43ac050557d357d3f2a53b1cb7f5c522-primary.sqlite.bz2
The rpm-ostree-libs package includes the shared library for rpm-ostree.