Failure to build flatpak

[orontee]

Context

Can't update io.github.orontee.Argos to use v1.16.0 sources since build of the flatpak image is broken, cf. https://github.com/flathub-infra/vorarbeiter/actions/runs/14783298012/job/41506786419

Analysis

Reproduced localy:

$ flatpak-builder --user --install --force-clean builddir io.github.orontee.Argos.json
...
Running: pip3 install --verbose --exists-action=i --no-index --find-links="file://${PWD}" --prefix=${FLATPAK_DEST} "attrs==24.2.0" --no-build-isolation
Using pip 25.0.1 from /usr/lib/python3.11/site-packages/pip (python 3.11)
Looking in links: file:///run/build/python3-attrs
Processing ./attrs-24.2.0-py3-none-any.whl
Installing collected packages: attrs
  Attempting uninstall: attrs
    Found existing installation: attrs 25.3.0
    Uninstalling attrs-25.3.0:
ERROR: Could not install packages due to an OSError.
Traceback (most recent call last):
  File "/usr/lib/python3.11/shutil.py", line 853, in move
    os.rename(src, real_dst)
OSError: [Errno 18] Invalid cross-device link: '/usr/lib/python3.11/site-packages/attr/__init__.py' -> '/tmp/pip-uninstall-j1du_fgn/__init__.py'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.11/site-packages/pip/_internal/commands/install.py", line 458, in run
    installed = install_given_reqs(
                ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pip/_internal/req/__init__.py", line 65, in install_given_reqs
    uninstalled_pathset = requirement.uninstall(auto_confirm=True)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pip/_internal/req/req_install.py", line 723, in uninstall
    uninstalled_pathset.remove(auto_confirm, verbose)
  File "/usr/lib/python3.11/site-packages/pip/_internal/req/req_uninstall.py", line 370, in remove
    moved.stash(path)
  File "/usr/lib/python3.11/site-packages/pip/_internal/req/req_uninstall.py", line 261, in stash
    renames(path, new_path)
  File "/usr/lib/python3.11/site-packages/pip/_internal/utils/misc.py", line 350, in renames
    shutil.move(old, new)
  File "/usr/lib/python3.11/shutil.py", line 874, in move
    os.unlink(src)
OSError: [Errno 30] Read-only file system: '/usr/lib/python3.11/site-packages/attr/__init__.py'
Error: module python3-attrs: Le processus fils s’est terminé avec le code 1

[orontee]

See https://github.com/flathub/io.github.orontee.Argos/pull/22/commits/659032c965bb5aaf62d588d7c6bc6cf4e2786479