It seems necessary to pass test-bundled-gems with REXML.

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

	Clear runtime dependencies if default gems is specified.

	The current build system uses runtime dependencies from only
	`.bundle` directory. We shouldn't install runtime dependencies
	from rubygems.org when `make test-bundled-gems` is invoked.

	Fixed dependencies list format

	Don't need to remove ruby2_keywords dependency from drb

	Re-use strscan with ruby repo

	Don't create T_MATCH object if /regexp/.match(string) doesn't match

	Fixes [Bug #20104]
	---
	 re.c                     |  9 ++++++---
	 test/ruby/test_regexp.rb | 12 ++++++++++++
	 tool/lib/envutil.rb      |  8 ++++++++
	 3 files changed, 26 insertions(+), 3 deletions(-)

It was renamed from test_mjit, but we did not maintain it as test_rjit.
We test RJIT very differently.

This commit adds `GC.auto_compact = :empty` which will run
auto-compaction sorting pages by empty slots so the most amount of
objects will be moved. This will make it easier to write tests for
auto-compaction.

```
.../tool/lib/colorize.rb:56:in `resolve_color': undefined method `gsub' for an instance of Symbol (NoMethodError)

    color.gsub(/\b[a-z][\w ]+/) do |n|
	 ^^^^^
	from .../tool/lib/colorize.rb:47:in `decorate'
	from .../tool/lib/test/unit.rb:1012:in `block in failed'
```

Not only:
```
$ ruby colorize.rb fail foo
```

Also:
```
$ ruby colorize.rb 'bright_blue;bold' foo
```