Work correctly on jruby and when ruby is installed under another name

[jeremyevans]

Borrow the code rake uses for FileUtils::RUBY to get the path to
the current ruby binary.

Force the mt argument to be an array of strings, as shelljoin does
not work if an element of the array is an integer on JRuby.

[zenspider]

1. Where is this RUBY constant defined?
2. You're saying that jruby's shellword's shelljoin doesn't to_s? seems like a bug.

[zenspider]

Verified it's a bug. Filing a ticket on jruby.

[zenspider]

I'm not comfortable with the RUBY bit yet. The rest makes sense for the jruby bug.

10004 % ruby -rshellwords -e 'p RUBY'
-e:1:in `<main>': uninitialized constant RUBY (NameError)

[jeremyevans]

The RUBY implementation I borrowed from rake is located at https://github.com/ruby/rake/blob/master/lib/rake/file_utils.rb#L9

I just copied the code and placed it inside Minitest::Bisect: https://github.com/seattlerb/minitest-bisect/pull/4/files#diff-ef8f6d7f169542f4c0a72cc6b77c42e7R12

Even though the JRuby bug may be fixed in JRuby's master branch, it still exists in the latest official release, so it may be worth including the workaround so that people using JRuby 1.6 or 1.7 can still use minitest-bisect.

[zenspider]

NOPE. Ignore me. The patch partially rejected because I applied your previous patch and the hunk was in-between. Found the reject, carved it up and manually applied it.

[zenspider]

merged. Thanks!