[rubygems/rubygems] Use `SystemExit#status` as `exit_code`

No reasons to manage separately.

https://github.com/rubygems/rubygems/commit/8ede5c886e

lib/rubygems/exceptions.rb

@@ -221,14 +221,12 @@ class Gem::SystemExitException < SystemExit
   ##
   # The exit code for the process
 
-  attr_accessor :exit_code
+  alias exit_code status
 
   ##
   # Creates a new SystemExitException with the given +exit_code+
 
   def initialize(exit_code)
-    @exit_code = exit_code
-
     super exit_code, "Exiting RubyGems with exit_code #{exit_code}"
   end
 end

test/rubygems/test_exit.rb

@@ -8,4 +8,10 @@ class TestExit < Gem::TestCase
     system(*ruby_with_rubygems_in_load_path, "-e", "raise Gem::SystemExitException.new(2)")
     assert_equal 2, $?.exitstatus
   end
+
+  def test_status
+    exc = Gem::SystemExitException.new(42)
+    assert_equal 42, exc.status
+    assert_equal 42, exc.exit_code
+  end
 end