The rpm-ostree-devel package includes the header files for rpm-ostree-libs.
acquired package info from repodata DB: repodata/3ca3f05b705ac87dba48cdb0fbc8de8608778488df6909ce1c87b6d6b650a769-primary.sqlite.bz2
The rpm-ostree-libs package includes the shared library for rpm-ostree.