ci: Init packages' Derivation

[haruki7049]

Why did I created this pull request?

ビルトをNixに任せる事で、CIを楽にする魂胆。

[haruki7049]

cdf4420
このコミットにて、以下のエラーが発生。

error:
       … while calling the 'derivationStrict' builtin

         at /builtin/derivation.nix:9:12: (source not available)

       … while evaluating derivation 'gateway-0.1.0'
         whose name attribute is located at /nix/store/fjs1x9gz2n1dvjqcyyl6qsw110qxc2zn-source/pkgs/stdenv/generic/make-derivation.nix:331:7

       … while evaluating attribute 'cargoArtifacts' of derivation 'gateway-0.1.0'

         at /nix/store/yvwj0z0s968lm1ll8kh99yvf6isp37wb-source/lib/mkCargoDerivation.nix:59:10:

           58| } // {
           59|   inherit cargoArtifacts;
             |          ^
           60|

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: unable to find Cargo.lock at /nix/store/dwx62imnynz0d0l70pjjsm7m9n9bi8wh-gateway. please ensure one of the following:
       - a Cargo.lock exists at the root of the source directory of the derivation,
         it is *not* included in .gitignore, and that it is at least staged with git
         via `git add -N Cargo.lock`
       - set `cargoVendorDir = vendorCargoDeps { cargoLock = ./some/path/to/Cargo.lock; }`
       - set `cargoVendorDir = vendorCargoDeps { src = ./src/containing/cargo/lock/file; }`
       - set `cargoVendorDir = null` to skip vendoring altogether

このエラーの内容を要約すると、指定されたパスの中にCargo.lockが無いというエラーっぽい。かと言って、gatewayとsutera-libは違うクレートだし、どうしたら良いか分からない…。