Shrike [1] filed a deletion request for capnproto-compiler-git [2]: Obsolete package. Cap'n Proto has been rewritten in C++ and the up to date packages can be found at: https://aur.archlinux.org/packages/capnproto/ https://aur.archlinux.org/packages/capnproto-git/
[1] https://aur.archlinux.org/account/Shrike/ [2] https://aur.archlinux.org/pkgbase/capnproto-compiler-git/
