fix: patch RPATH on staged libs to fix libvirt_iohelper missing libxml2

[hemanthnakkina]

libvirt_iohelper is spawned by virFileWrapperFdNew() with a minimal environment containing only LIBVIRT_LOG_OUTPUTS=1:stderr. The parent libvirtd's LD_LIBRARY_PATH is never propagated to the child, so staged shared libraries (libxml2, libyajl, libicuuc, etc.) in usr/lib/x86_64-linux-gnu/ are not found, causing server suspend to fail:

operation failed: .../libvirt_iohelper: error while loading shared
libraries: libxml2.so.2: cannot open shared object file: No such
file or directory

Fix by adding build-attributes: [enable-patchelf] to the libvirt part.
Snapcraft sets RPATH (old DT_RPATH tag, not RUNPATH) with $ORIGIN on
libvirt-built ELF files, enabling the dynamic linker to locate staged
libraries transitively — without requiring a build-time patchelf script.

Fixes: https://bugs.launchpad.net/snap-openstack/+bug/2150555

Assisted-by: Claude:claude-4.6-sonnet

[Copilot]

Pull request overview

This PR updates the snap build to ensure libvirt_iohelper can reliably resolve staged shared-library dependencies at runtime (without relying on LD_LIBRARY_PATH) by embedding an RPATH into staged ELF shared libraries during the prime step.

Changes:

• Add patchelf as a build dependency for the libvirt part.
• Add an override-prime step that uses patchelf to add an arch-aware RPATH pointing at /snap/<name>/current/usr/lib/<multiarch-triplet> for staged shared libraries under usr/lib.

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[gboutry]

I wonder if this cannot be solved from updating the build command?

https://documentation.ubuntu.com/snapcraft/stable/how-to/debugging/use-the-classic-linter/

[hemanthnakkina]

I wonder if this cannot be solved from updating the build command?

https://documentation.ubuntu.com/snapcraft/stable/how-to/debugging/use-the-classic-linter/

Yes it worked.. pushed the new change