use a local git+file pin

[reynir]

No description provided.

[github-actions]

  0.00 %      0/21     src/cc_message.ml
 80.42 %   1483/1844   src/config.ml
 60.59 %    123/203    src/config_ext.ml
 72.85 %   1001/1374   src/engine.ml
100.00 %      0/0      src/miragevpn.ml
 92.88 %    365/393    src/packet.ml
 20.00 %      1/5      src/result.ml
 82.72 %     67/81     src/state.ml
 62.93 %    146/232    src/tls_crypt.ml
 76.72 %   3186/4153   Project coverage

[hannesm]

thanks.