Use custom rust nightly image with cargo-cov and clippy pre-installed

ci/buildkite.yml

@@ -7,7 +7,7 @@ steps:
   - command: "ci/shellcheck.sh"
     name: "shellcheck [public]"
     timeout_in_minutes: 20
-  - command: "ci/docker-run.sh rustlang/rust:nightly ci/test-nightly.sh"
+  - command: "ci/docker-run.sh solanalabs/rust-nightly ci/test-nightly.sh"
     name: "nightly [public]"
     env:
       CARGO_TARGET_CACHE_NAME: "nightly"

ci/docker-rust-nightly/Dockerfile

@@ -0,0 +1,3 @@
+FROM rustlang/rust:nightly
+
+RUN cargo install --force clippy cargo-cov

ci/docker-rust-nightly/README.md

@@ -0,0 +1,3 @@
+Docker image containing rust nightly and some preinstalled crates used in CI.
+This image must be manually updated periodically by running `./build.sh` with
+after logging into https://hub.docker.com/u/solanalabs/

ci/docker-rust-nightly/build.sh

@@ -0,0 +1,6 @@
+#!/bin/bash -ex
+
+cd "$(dirname "$0")"
+
+docker build -t solanalabs/rust-nightly .
+docker push solanalabs/rust-nightly

ci/test-nightly.sh

@@ -18,7 +18,6 @@ _ cargo test --verbose --features unstable
 exit 0
 
 # Coverage disabled (see issue #433)
-_ cargo install --force cargo-cov
 _ cargo cov test
 _ cargo cov report