Set the Rails environment from an environment variable

Option parsing happens too late to have any impact on the Rails
environment.  Rails accesses the environment name and memoizes it too
early in the boot process for a commandline option to have any impact on
the database connection, so we'll change this test to set the
environment from an environment variable (and ensure it still works when
running tests with `ruby`)

railties/lib/rails/test_unit/runner.rb

@@ -12,11 +12,8 @@ module Rails
 
       class << self
         def attach_before_load_options(opts)
-          ENV["RAILS_ENV"] = "test"
           opts.on("--warnings", "-w", "Run with Ruby warnings enabled") {}
-          opts.on("-e", "--environment ENV", "Run tests in the ENV environment") { |e|
-            ENV["RAILS_ENV"] = e
-          }
+          opts.on("-e", "--environment ENV", "Run tests in the ENV environment") {}
         end
 
         def parse_options(argv)

railties/test/application/test_runner_test.rb

@@ -593,7 +593,7 @@ module ApplicationTests
 
       file = create_test_for_env("development")
       results = Dir.chdir(app_path) {
-        `ruby -Ilib:test #{file} -e development`.each_line.map { |line| JSON.parse line }
+        `RAILS_ENV=development ruby -Ilib:test #{file}`.each_line.map { |line| JSON.parse line }
       }
       assert_equal 1, results.length
       failures = results.first["failures"]