Tracing ActiveRecord if ActiveSupport is present

If the suite that’s being monitored doesn’t have ActiveSupport, then it
definitely doesn’t have ActiveRecord, and so no tracing is required.

lib/buildkite/test_collector.rb

@@ -12,8 +12,6 @@ module TestCollector
 require "timeout"
 require "tmpdir"
 
-require "active_support/notifications"
-
 require_relative "test_collector/version"
 require_relative "test_collector/error"
 require_relative "test_collector/ci"
@@ -70,6 +68,10 @@ def self.enable_tracing!
       Buildkite::TestCollector::Network.configure
       Buildkite::TestCollector::Object.configure
 
+      return unless defined?(ActiveSupport)
+
+      require "active_support/notifications"
+
       ActiveSupport::Notifications.subscribe("sql.active_record") do |name, start, finish, id, payload|
         Buildkite::TestCollector::Uploader.tracer&.backfill(:sql, finish - start, **{ query: payload[:sql] })
       end

spec/spec_helper.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "buildkite/test_collector"
+require "active_support/notifications"
 
 Dir["spec/support/**/*.rb"].each { |f| require File.expand_path(f) }