Build Omnibus for Ubuntu 26.04 (resolute)

What does this MR do?

Build Omnibus packages for Ubuntu 26.04 (resolute), following the same pattern used for Ubuntu 24.04 (noble) in !7668 (merged).

Changes:

• Add resolute codename mapping in OhaiHelper for Ubuntu 26.04
• Add branch, tag, staging, and release CI jobs in gitlab-ci-config/dev-gitlab-org.yml
• Add knapsack and spec jobs in gitlab-ci-config/gitlab-com.yml
• Add package check jobs in gitlab-ci-config/check-packages.yml
• Add gcc compiler override in config/software/libtensorflow_lite.rb for Ubuntu 26.04
• Add a patch for krb5 1.22.1 to fix const-correctness issues with glibc 2.42+

GCC 15 default on Ubuntu 26.04

Ubuntu 26.04 ships gcc 15 by default, but the maximum gcc version we currently support is 14. The builder image uses update-alternatives to switch to gcc 14 so that all components compile with a supported toolchain. The libtensorflow_lite patches (standard-ints, abseil, flatbuffers) are also applied for Ubuntu 26.04, matching the existing pattern for Debian 13 and AlmaLinux 10.

glibc 2.42+ const-correct strchr() family

Ubuntu 26.04 ships glibc 2.42+, which makes the strchr() family of functions const-correct under _GNU_SOURCE (i.e. they return const char * when given a const char * argument). This causes build failures in krb5 1.22.1 where char *cp = strchr(...) assignments now produce -Werror=discarded-qualifiers errors. A patch (config/patches/krb5/krb5-1.22.1-glibc-const-string.patch) adds explicit (char *) casts to the three affected call sites in ccbase.c, expand_path.c, and locate_kdc.c.

Changelog: added

Verification

builder update mr: Add Ubuntu 26 builder image and CI jobs (gitlab-omnibus-builder!483 - merged)

Trigger the pipeline with:

BUILDER_IMAGE_REGISTRY        = registry.gitlab.com/gitlab-org/gitlab-omnibus-builder/staging
PUBLIC_BUILDER_IMAGE_REGISTRY = registry.gitlab.com/gitlab-org/gitlab-omnibus-builder/staging
BUILDER_IMAGE_REVISION        = lucas-ubuntu-26-builder

Related issues

Closes #9819 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• MR title and description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• Latest Merge Result pipeline is green.
• When ready for review, MR is labeled workflowready for review per the Distribution MR workflow.
• The UBT version and corresponding checksum hash have been updated and referenced in the merge request if applicable.
  • UBT EE pipeline (Trigger:ee-package-ubt) is green

For GitLab team members

If you don't have access to this, the reviewer should trigger these jobs for you during the review process.

• The manual Trigger:ee-package jobs have a green pipeline running against latest commit.
  • To debug QA failures, refer to the Investigate QA failures section.
• If config/software or config/patches directories are changed, make sure the build-package-on-all-os job within the Trigger:ee-package downstream pipeline succeeded.
• If you are changing anything SSL related, then the Trigger:package:fips manual job within the Trigger:ee-package downstream pipeline must succeed.
• If CI configuration is changed, the branch must be pushed to dev.gitlab.org to confirm regular branch builds aren't broken.

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes.
• Documentation created/updated.
• Tests added.
• Integration tests added to GitLab QA.
• Equivalent MR/issue for the GitLab Chart opened.
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme[REDACTED]host:port may require quotation or other special handling when rendered in a template and written to a configuration file.

Note: This MR adds the omnibus-gitlab side of the changes. Builder images for Ubuntu 26.04 will need to be added to the gitlab-omnibus-builder project before the CI jobs can successfully build packages.