[CI] Moves lint and docs tasks to Buildkite

.buildkite/build-documentation.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+docker build --file .buildkite/Dockerfile --tag elastic/eland --build-arg PYTHON_VERSION=${PYTHON_VERSION} .
+docker run \
+       --name doc_build \
+       --rm \
+       elastic/eland \
+       sudo apt-get update && sudo apt-get install --yes pandoc && nox -s docs
+

.buildkite/lint-code.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+docker build --file .buildkite/Dockerfile --tag elastic/eland --build-arg PYTHON_VERSION=${PYTHON_VERSION} .
+docker run \
+       --name linter \
+       --rm \
+       elastic/eland \
+       nox -s lint

.buildkite/pipeline.yml

@@ -1,4 +1,14 @@
 steps:
+  - label: ":terminal: Lint code"
+    agents:
+      provider: "gcp"
+    commands:
+      - ./.buildkite/lint-code.sh
+  - label: ":books: Build documentation"
+    agents:
+      provider: "gcp"
+    commands:
+      - ./.buildkite/build-documentation.sh
   - label: "Eland :python: {{ matrix.python }} :elasticsearch: {{ matrix.stack }}"
     agents:
       provider: "gcp"