Use autorun when running via Rake.

Makes sure we get support for `Minitest.after_run` hooks and don't
accidentally run tests twice.

Requires overriding minitest `run` to respect the TESTOPTS variable.

railties/lib/rails/test_unit/minitest_plugin.rb

@@ -61,11 +61,21 @@ def self.plugin_rails_options(opts, options)
   # as the patterns would also contain the other Rake tasks.
   def self.rake_run(patterns) # :nodoc:
     @rake_patterns = patterns
-    passed = run(Shellwords.split(ENV["TESTOPTS"] || ""))
-    exit passed unless passed
-    passed
+    autorun
   end
 
+  module RunRespectingRakeTestopts
+    def run(args = [])
+      if defined?(@rake_patterns)
+        args = Shellwords.split(ENV["TESTOPTS"] || "")
+      end
+
+      super
+    end
+  end
+
+  singleton_class.prepend RunRespectingRakeTestopts
+
   # Owes great inspiration to test runner trailblazers like RSpec,
   # minitest-reporters, maxitest and others.
   def self.plugin_rails_init(options)