[CI] Run Danger with Bazel (#4138)

It'd be nice to avoid needing to maintain rbenv on CI

.buildkite/pipeline.yml

@@ -7,10 +7,10 @@ steps:
       - bazel test --test_output=errors //Tests/...
   - label: "Danger"
     commands:
-      - echo "--- Bundle Install"
-      - bundle install
+      - echo "--- Build Danger"
+      - bazel build danger
       - echo "+++ Run Danger"
-      - bundle exec danger --verbose
+      - bazel run danger --run_under="cd $PWD && " -- --verbose
   - label: "Analyze"
     commands:
       - echo "+++ Analyze"

BUILD

@@ -131,3 +131,13 @@ sh_test(
         ":swiftlint",
     ],
 )
+
+# Danger
+
+load("@bazelruby_rules_ruby//ruby:defs.bzl", "ruby_binary")
+
+ruby_binary(
+    name = "danger",
+    main = "@bundle//:bin/danger",
+    deps = ["@bundle//:bin"],
+)

WORKSPACE

@@ -48,3 +48,37 @@ http_archive(
 load("@com_github_buildbuddy_io_rules_xcodeproj//xcodeproj:repositories.bzl", "xcodeproj_rules_dependencies")
 
 xcodeproj_rules_dependencies()
+
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+
+git_repository(
+    name = "bazelruby_rules_ruby",
+    commit = "c93a6814b6193572c7c8b677b560314f52b31962",
+    remote = "https://github.com/bazelruby/rules_ruby.git",
+    shallow_since = "1651264604 -0700",
+)
+
+load(
+    "@bazelruby_rules_ruby//ruby:deps.bzl",
+    "rules_ruby_dependencies",
+    "rules_ruby_select_sdk",
+)
+
+rules_ruby_dependencies()
+
+load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
+
+bazel_skylib_workspace()
+
+rules_ruby_select_sdk(version = "host")
+
+load(
+    "@bazelruby_rules_ruby//ruby:defs.bzl",
+    "ruby_bundle",
+)
+
+ruby_bundle(
+    name = "bundle",
+    gemfile = "//:Gemfile",
+    gemfile_lock = "//:Gemfile.lock",
+)