The reason Azure Linux was never used previously for the source-build legs is that Azure Linux doesn't source build .NET. Using a distro that source builds .NET is more advantageous. Based on that reasoning, I am not in favor of this change.

ok but didn't we already go that way when we merged #16456 ?
this is basically for the cases where we run on the host directly (which we don't expect to happen a lot, unless it's managed code where the OS difference doesn't really matter).

ok but didn't we already go that way when we merged #16456 ? this is basically for the cases where we run on the host directly (which we don't expect to happen a lot, unless it's managed code where the OS difference doesn't really matter).

You are right, this is about the build agent. The container is what is really important here barring the issue described in dotnet/source-build#5463

/backport to release/10.0

Started backporting to release/10.0 (link to workflow run)

@akoeplinger backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Use AzureLinux3 image for source-build.yml
Using index info to reconstruct a base tree...
M	eng/common/core-templates/job/source-build.yml
Falling back to patching base and 3-way merge...
Auto-merging eng/common/core-templates/job/source-build.yml
CONFLICT (content): Merge conflict in eng/common/core-templates/job/source-build.yml
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Use AzureLinux3 image for source-build.yml
Error: The process '/usr/bin/git' failed with exit code 128