unresolved import pkg_config

[fbartels]

Hi, when compiling the server (through the compose file, namely with docker-compose build) the build errors out with the following error message:

   Compiling mysqlclient-sys v0.2.4
   Compiling libsqlite3-sys v0.12.0
error[E0432]: unresolved import `pkg_config`
  --> /usr/local/cargo/registry/src/github.com-1ecc6299db9ec823/libsqlite3-sys-0.12.0/build.rs:97:9
   |
97 |     use pkg_config;
   |         ^^^^^^^^^^ no `pkg_config` in the root

error[E0658]: non-reference pattern used to match a reference (see issue #42640)
   --> /usr/local/cargo/registry/src/github.com-1ecc6299db9ec823/libsqlite3-sys-0.12.0/build.rs:115:13
    |
115 |             Ok(v) if v != "0" => "static",
    |             ^^^^^ help: consider using a reference: `&Ok(v)`

error: aborting due to 2 previous errors

error: Could not compile `libsqlite3-sys`.
warning: build failed, waiting for other jobs to finish...
error: failed to compile `diesel_cli v1.4.0`, intermediate artifacts can be found at `/tmp/cargo-install.SKWvFNhLWVoi`

Caused by:
  build failed

[dstar4138]

Apologies, I haven't been as attentive to GitHub issues for quite a while as I should be.

Thank you for trying this project out, and I'll see about a resolution for this.

I wonder if the docker versions switched out from under me?