[Bug]: riscv64 remote builds fail when packing the final squashfs image

[NucciTheBoss]

The Slurm snap currently fails to build/pack on riscv64. The build gets all the way to the end but then fails to create the final squashfs image:

Creating snap package...
Command '['snap', 'pack', '--filename', 'slurm_23.11.1_riscv64.snap', '--compression', 'lzo', PosixPath('/build/slurm/prime'), PosixPath('/build/slurm')]' returned non-zero exit status 20.
Full execution log: '/root/.local/state/snapcraft/log/snapcraft-20240528-134314.843534.log'
Build failed
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/lpbuildd/target/build_snap.py", line 308, in run
    self.build()
  File "/usr/lib/python3/dist-packages/lpbuildd/target/build_snap.py", line 292, in build
    self.run_build_command(["snapcraft"], cwd=output_path, env=env)
  File "/usr/lib/python3/dist-packages/lpbuildd/target/operation.py", line 62, in run_build_command
    return self.backend.run(args, cwd=cwd, env=full_env, **kwargs)
  File "/usr/lib/python3/dist-packages/lpbuildd/target/lxd.py", line 718, in run
    subprocess.check_call(cmd, **kwargs)
  File "/usr/lib/python3.10/subprocess.py", line 369, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['lxc', 'exec', 'lp-noble-riscv64', '--env', 'LANG=C.UTF-8', '--env', 'SHELL=/bin/sh', '--env', 'http_proxy=http://10.10.10.1:8222/', '--env', 'https_proxy=http://10.10.10.1:8222/', '--env', 'GIT_PROXY_COMMAND=/usr/local/bin/lpbuildd-git-proxy', '--env', 'SNAPPY_STORE_NO_CDN=1', '--env', 'SNAPCRAFT_BUILD_INFO=1', '--env', 'SNAPCRAFT_IMAGE_INFO={"build-request-id": "lp-89355112", "build-request-timestamp": "2024-05-28T13:04:52Z", "build_url": "https://launchpad.net/~build.snapcraft.io/+snap/a538afbd6f26d0f2f7ac6474c6c680db/+build/2495044"}', '--env', 'SNAPCRAFT_BUILD_ENVIRONMENT=host', '--env', 'SNAPCRAFT_BUILD_FOR=riscv64', '--', '/bin/sh', '-c', 'cd /build/slurm && linux64 snapcraft']' returned non-zero exit status 1.
Revoking proxy token...
RUN: /usr/share/launchpad-buildd/bin/in-target scan-for-processes --backend=lxd --series=noble --arch=riscv64 SNAPBUILD-2495044
Scanning for processes to kill in build SNAPBUILD-2495044

Unfortunately, the logs are not that helpful for figuring out what when wrong, so we'll need to reproduce the issue in a local riscv64 builder to get more granular feedback from snapcraft.