[steveisok]

Summary

Update the Linux x64 developer-innerloop build container from Ubuntu 24.04 to Ubuntu 26.04. Keep this lane on Ubuntu as a proxy for Ubuntu desktop and WSL development, rather than moving it to Azure Linux.

Use the published native-prerequisite image, pinned to its verified Linux AMD64 manifest:

mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-amd64@sha256:9652406444a2d3527125566f0787ba0839efca9d009de374a3efc22570f19501

Remove the AL4-specific dependency-installer step added in the initial revision. The Ubuntu prerequisite image already supplies the native toolchain and development headers, so no per-job package installation is added. The net PR diff is only the linux_x64_dev_innerloop image/digest update in pipeline-with-resources.yml; global-build-job.yml returns to its original contents.

Preserve native/non-cross build commands, AL3 build.azurelinux.3.amd64[.open] build-agent hosts, target sysroots and ABI policy, SDK pins, and all unrelated image pins. No cross-build image or ARM64 image is substituted.

Related to #136313, I1 only. This does not close the tracking issue or declare I1 complete.

Local validation

Tested the actual pinned Linux AMD64 Ubuntu image under emulation on an ARM64 Docker Desktop host, not on a native x64 machine. The image identifies as Ubuntu 26.04.1 LTS.

Startup, packaged-toolchain and development-package checks passed. The image supplies Clang/LLVM 18.1.8, GCC 15.2.0, CMake 4.2.3, Ninja 1.13.2, and the ICU/OpenSSL/Kerberos/LTTng development dependencies used by the smoke. No packages were installed in the test container.

A small external CMake harness built the repository's minipal and C/C++ smoke executables:

• /runtime/eng/native/gen-buildsys.sh /evidence/native /evidence/native-build x64 linux clang Debug ninja - passed using the repository's existing compiler/CMake setup.
• cmake --build /evidence/native-build --target minipal_smoke dependencies_smoke --parallel 2 - passed, 26 build actions.
• ctest --test-dir /evidence/native-build --output-on-failure --verbose - 2 passed, 0 failed. The C executable exercised ICU 78.2, OpenSSL 3.5.5 digest generation and Kerberos initialization, with LTTng headers/linkage. The C++ executable exercised minipal random generation, page size, UTF-8 roundtripping and std::thread.

Both executables were verified as AMD64 ELF binaries and ran successfully. CMake reported CMAKE_CROSSCOMPILING=FALSE, x86_64 host/target processors and an empty CMAKE_SYSROOT.

The exercised mkdir -p, CMake configure/build and CTest operations did not encounter the known Docker Desktop openat2 limitation. No validation shim, Docker/binfmt/kernel reconfiguration, or tracked workaround was used. Static YAML/image/consumer assertions and git diff --check passed; the net image-only diff and removal of the prior bootstrap were checked against the original PR baseline.

No full product build, broad test matrix, Azure Pipelines template expansion or native x64 build-agent/container integration run was performed locally. Earlier AL4 results are not validation of this Ubuntu revision. The small emulated smoke does not establish full innerloop coverage.

Required native non-cross CI coverage

All three affected runtime-dev-innerloop jobs remain required for this revision:

• RuntimeFlavor_Mono
• CoreLib_Libraries_AnalyzersLinker
• Tools_AnalyzersLinker

Note

This change and PR description were prepared with GitHub Copilot.

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[agocke]

This is one I actually think we should keep on ubuntu. No one uses Azure Linux on the desktop, so we should keep Ubuntu as a dev proxy.

[jkoritzinsky]

Yeah this lane is very specifically supposed to be on Ubuntu as that's the default WSL distro so that's what most people will use on their local machines.

Updated to use ubuntu 26.04

[steveisok]

/ba-g SOS tests already fixed by dotnet/diagnostics#6143