Migrate clang/llvm to build images

[mikebeaton]

Description

This PR proposes moving clang+llvm from -dev to -build, with a view to making a future PR offering CLANGDWARF and CLANGPDB CI to EDK 2.

I note that gcc in the Ubuntu image uses update-alternatives to link to a fixed version - while this is potentially somewhat fragile (i.e. there is unfortunately no automatic way to link all and only the bins provided by a given version), it does allow a fixed version. On the other hand the Fedora image doesn't use anything similar.

I haven't added a fixed version with update-alternatives for clang in the Ubuntu image, though am happy to update the PR do so; with either the bins which appear to be needed to build, or all bins which seem to be provided with the given version - although this is quite an extensive list in the case of llvm-14 (75 bins).

Issue #99

Containers Affected

ubuntu-22-build ubuntu-22-test ubuntu-22-dev fedora-40-build fedora-40-test fedora-40-dev

[mikebeaton]

I believe fedora-37-test is currently used for all EDK 2 CI https://github.com/tianocore/edk2/blob/master/.azurepipelines/templates/defaults.yml#L12 - specifically, for the CI which runs as Ubuntu-GCC5 - so possibly only fedora-40 would need this update?

[osteffenrh]

Here is the PR that switches the CI to the Fedora 40 image: https://github.com/tianocore/edk2/pull/6261

[mikebeaton]

The default gcc for Ubuntu 22.04 is 11, so I guess the update-alternatives links are required, if gcc 12 is required. On the other hand, AFACIT gcc 11 builds everything in EDK 2 fine... The default clang for Ubuntu 22.04, version 14, also builds EDK 2 fine, so I can't see a need to use update-alternatives there - but then again, I cannot yet clearly see what the original need was for update-alternatives for gcc. I don't know if @jgarver can comment?

[jgarver]

It was just to match the version of GCC in the Fedora images.

[mikebeaton]

It was just to match the version of GCC in the Fedora images.

Thanks for the response. Possibly it is more 'useful' (e.g. for CI), in that case, to find out whether things build or not in the default current gcc in Ubuntu? (In fact, they do!)

[jgarver]

"Building" and "working" are two different things.

I don't recall any specific issues with the default GCC on Ubuntu22, but I know we (NVIDIA) couldn't use the default GCC-9 in Ubuntu20. That's probably where the habit of using update-alternative began. The code originated with Ubuntu20 and was carried forward to Ubuntu22.

Anyway, I recommend:

• Keeping GCC as is in Ubuntu22.
• Not using update-alternative for clang, until we find a reason to not like the default version.
• Trying to move to the default GCC when we add Ubuntu24 support.

Of course, that means deviating from Fedora. But from what I've seen, Fedora is a faster moving target and Ubuntu won't keep up anyway.