add M1 pipeline on Buildkite

.buildkite/pipeline.yml

@@ -0,0 +1,12 @@
+steps:
+  - label: ":hammer: Specs"
+    commands:
+      - echo "--- Initialize git"
+      - git submodule update --init
+      - ./.github/scripts/setup_test_repo.sh
+      - echo "--- Bundler"
+      - gem install bundler:1.17.3
+      - bundle config path vendor/bundle
+      - bundle install --jobs 4 --retry 3 --without debugging documentation
+      - echo "+++ Run Specs"
+      - bundle exec rake spec

.github/scripts/setup_test_repo.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
 cd spec/fixtures/spec-repos/test_repo
+rm -rf .git || true
 git init
 git remote add origin https://bitbucket.com/test/test_repo.git

.gitignore

@@ -13,6 +13,7 @@ coverage/
 .idea/
 documentation/
 .bundle/
+vendor/bundle
 
 # trunk source
 spec/fixtures/spec-repos/trunk/**/*.etag