Ruby

TestRubyOptions#test_kanji fails on icc-x64 chkbuild.

From http://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-trunk/log/20161117T010002Z.fail.html.gz:

 1) Failure: TestRubyOptions#test_kanji [/home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/test/ruby/test_rubyoptions.rb:143]: 1. [1/2] Assertion for "stdout" | <["EUC-JP"]> expected but was | <[]>. 2. [2/2] Assertion for "stderr" | <[]> expected but was | <["/home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:279:in `gsub': invalid byte sequence in EUC-JP (ArgumentError)", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:279:in `expand'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:297:in `block in <module:RbConfig>'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:296:in `each_value'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:296:in `<module:RbConfig>'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/rbconfig.rb:10:in `<top (required)>'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/lib/rubygems.rb:9:in `require'", | "\tfrom /home/chkbuild/chkbuild/tmp/build/20161117T010002Z/ruby/lib/rubygems.rb:9:in `<top (required)>'", | "\tfrom <internal:gem_prelude>:4:in `require'", | "\tfrom <internal:gem_prelude>:4:in `<internal:gem_prelude>'"]>. 

This is because RbConfig::CONFIG["CC_VERSION_MESSAGE"] contains non-ASCII characters,
and can be fixed by adding a magic comment to rbconfig.rb.

But which encoding should be specified?

Possible options are:

1. ASCII-8BIT. It's reasonable when we can't know the correct encoding,
   but there may be compatibility issues.
2. UTF-8. UTF-8 is the default source encoding, so there is no compatibility issue
   because the current behavior when -K is specified is a run-time error.
3. The encoding of the locale at the time when ruby is compiled.