There is https://gitweb.gentoo.org/repo/gentoo.git/tree/app-emulation/lxc/lxc-3.1.0-r1.ebuild
and https://linuxcontainers.org/lxc/downloads/
That is, the lxc source tarball for liblxc also adds the command-line tools.
But to compile just the library and avoid the command-line tools, you would need to --enable-tools=no.