some pins missing

These are the pins that are needed if you are using an ARM processor. The first one may need removing and reinstalling.
$ opam pin mirage https://github.com/talex5/mirage.git#link_c_stubs
$ opam pin mirage-xen https://github.com/mirage/mage-platform
$ opam pin tcpip https://github.com/talex5/mirage-tcpip.git#checksum