Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

The `parse_make_command_line` in `assert_contains_make_command` fails to get
the make targets correctly, when the make command is set with make options by
environment variable such as `export make='make -j2'` at
lib/rubygems/ext/builder.rb::make.

So, we include the make options (eg, -XX) as a part of the command to fix the
case. Note that this commit still doesn't fix the case of
`export make='make -j 2'`.

https://github.com/rubygems/rubygems/commit/7730ef3fa0

This changes "test/rubygems/test_case.rb" to "test/rubygems/helper.rb",
and "test/rubygems/test_utilities.rb" to "test/rubygems/utilities.rb".

The two files are a helper for tests, not test files. However, a file
starting with "test_" prefix is handled as a test file directly loaded
by test-unit because Rakefile specifies:

```
t.test_files = FileList['test/**/test_*.rb']
```

Directly loading test/rubygems/test_utilities.rb caused "uninitialized
constant Gem::TestCase". This issue was fixed by
59c682097197fee4052b47e4b4ab86562f3eaa9b, but the fix caused a
"circular require" warning because test_utilities.rb and test_case.rb
are now requiring each other.

Anyway, adding "test_" prefix to a test helper file is confusing, so
this changeset reverts the fix and solve the issue by renaming them.

https://github.com/rubygems/rubygems/commit/6460e018df

https://github.com/rubygems/rubygems/commit/c77868a555

https://github.com/rubygems/rubygems/commit/0b145135c7

https://github.com/rubygems/rubygems/commit/769e87f011

https://github.com/rubygems/rubygems/commit/a7c93558c3