Add toolchain_utils@1.0.0-alpha.16

[mattyclarkson]

A ruleset to simplify the creation of Bazel toolchains, eliminating as much boilerplate as possible.

For a real-world example of usage, see rules_coreutils

See the project README for more information.

This requires #1284 as the source tarball comes from a non-GitHub endpoint and does not use a sha256 integrity.

[mattyclarkson]

First PR here, so bear with me whilst I get most things correct in presubmit.yml and sort out the validation checks.

[mattyclarkson]

I'm hitting a self-signed certificate error on Windows.

* Download and unpack https://gitlab.arm.com/bazel/rules_toolchain/-/releases/v1.0.0-alpha.13/downloads/src.tar.gz
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain

I'm not aware that we are using a self-signed certificate.

The source archive download is working on other platforms, so a little confused why this is failing on Windows.

I will attempt to debug inside Windows Sandbox.

[mattyclarkson]

Reproduced the certificate failure inside Windows Sandbox, which does not have the Arm self-signed certificates installed.

from urllib.request import urlopen
with urlopen("https://gitlab.arm.com/bazel/rules_toolchain/-/releases/v1.0.0-alpha.13/downloads/src.tar.gz") as stream:
    stream.read()

I'll pick up with our team to figure out how to remove that restriction on our certificate.

This only happens within Python. Using Powershell to retrieve the source tarball is fine so it will require more understanding to unlock the Windows CI run on ourside.

Until then, I'll comment out the Windows CI job.

[mattyclarkson]

RFC: @fmeum / @meteorcloudy

[meteorcloudy]

I have no extra input for the Windows failure. Overall looks good if we can resolve the naming issue ;)