Add CI script to check line ends

[wks]

We add CI scripts to ensure that all text files

• use UNIX line ends (LF only), and
• have a newline character at the end of the file.

This PR is inspired by the scripts introduced in the OpenJDK binding in mmtk/mmtk-openjdk#105, but also offers the ability to automatically fix line ends for the user:

./.github/scripts/ci-check-lineends.sh -f

This PR also fixes existing text files that have wrong line ends.

[wks]

The dos2unix --info=e option is only available since version 7.5.2.

The dos2unix --add-eol option is only available since version 7.5.0.

But Ubuntu 22.04 (on which we run mmtk-core CI tests) only provides dos2unix 7.4.2, and Ubuntu 24.04 only provides 7.5.1. This means we won't be able to implement line-end checking/fixing using dos2unix until we switch to the not-yet-released Ubuntu 26.04 image, or install dos2unix manually.

[wks]

As we can see in #1453, the CI style check will now fail if any text file has wrong line ending style.

We may introduce .gitattributes later (see #1418 (comment)). We can discuss later whether we use that list for determining which file to check, or we maintain .gitattributes and ci-check-lineends.sh separately.

[qinsoon]

LGTM

[qinsoon]

I don't think we want -v. From the log in https://github.com/mmtk/mmtk-core/actions/runs/22472311227/job/65091763326?pr=1453, without -v, we will skip printing "Processing file" lines, and the output will only show the files that violate the check, which is much cleaner and useful.

[wks]

Yes. That makes sense. I just tried to mimic the style of our existing bash scripts which use -x. I think it is cleaner to just print files with errors.