build via container cleanups

[dustymabe]

A few cleanups I've been carrying locally for a while. See individual commit messages:

commit 1104bc4423ce7dd649513d3570020ec35e1180c4 (HEAD -> dusty-build-via-container-cleanups, origin/dusty-build-via-container-cleanups)
Author: Dusty Mabe <[email protected]>
Date:   Wed Sep 10 14:57:15 2025 -0400

    cmd-build-with-buildah: selectively source NAME from argsfile
    
    In [1] we added `DESCRIPTION=Fedora CoreOS testing-devel` to
    build-args.conf, but this isn't exactly proper bash syntax.
    Bash would want `Fedora CoreOS testing-devel` to be in quotes,
    but `podman`/`docker` don't really support that in env file [2] [3]
    and I assume args file is the same. If I added quotes there I get
    "org.opencontainers.image.description": "\"Fedora CoreOS branched\"".
    
    [1] https://github.com/coreos/fedora-coreos-config/commit/90109c41d4fcfba7c7f2546df49a827f305be245
    [2] https://github.com/containers/podman/issues/9446
    [3] https://github.com/docker/for-linux/issues/1208

commit 651b578815ee02b5e3272a5ce95df80966bca7b6
Author: Dusty Mabe <[email protected]>
Date:   Mon Aug 25 15:34:29 2025 -0400

    cmd-build-with-buildah: clean up overrides repo metadata
    
    If there are no rpms then let's clean up the repo metadata if
    it exists which should prevent cosmetic warts like:
    
    ```
    Updating and loading repositories:
     overrides                              ???% |   0.0   B/s |  -1.0   B |  ?
    >>> Curl error (37): Could not read a file:// file for file:///run/src/overrides
    >>> Usable URL not found
    ```
    
    Or fatal ones like:
    
    ```
    error: Installing packages: importing RPMs: failed to open /run/src/overrides/rpm/systemd-258~rc3-2.fc44.x86_64.rpm
    ```

commit d67d9d0c79cfb7e746da20218c2a02f1d9b07b6a
Author: Dusty Mabe <[email protected]>
Date:   Tue Aug 26 13:32:20 2025 -0400

    cmdlib: specify repo path for import_oci_archive()
    
    Somehow hardcoding `tmp/repo` here isn't actually working. Here's
    what happens if I blow away my `tmp/` and then attempt to do another
    operation (like `cosa osbuild qemu`):
    
    ```
    Wrote: ostree-unverified-image:oci-archive:/srv/tmp/cosa-import-op0cg6_c/out.ociarchive => e202ee3cb8a2a8d814bd2b325cdef5500459fd2381d4fa766cd15ab730ae0e80
    2273 metadata, 8746 content objects imported; 1.2 GB content written
    1471 metadata, 1534 content objects imported; 133.6 MB content written
    Imported OCI image as build 42.20250821.dev.0
    Pruning build 44.20250826.dev.0
    Deleting 5 blob refs
    [coreos-assembler]$
    [coreos-assembler]$ rm -rf tmp/*
    [coreos-assembler]$ cosa osbuild qemu
    Config commit: e5f88e72120b3f89cf2c4d81b45bbe791d9bd79d
    Using manifest: /srv/src/config/manifest.yaml
    Will build qemu
    Extracting e202ee3cb8a2a8d814bd2b325cdef5500459fd2381d4fa766cd15ab730ae0e80
    layers already present: 0; layers needed: 66 (975.9 MB)
    3725 metadata, 21742 content objects imported; 1.7 GB content written                                                                                                                       3
    2603 metadata, 10508 content objects imported; 250.5 MB content written
    error: No such metadata object e202ee3cb8a2a8d814bd2b325cdef5500459fd2381d4fa766cd15ab730ae0e80.commit
    Traceback (most recent call last):
      File "<string>", line 10, in <module>
        cmdlib.import_ostree_commit(workdir, builddir, buildmeta, extract_json=('1' == '1'))
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/usr/lib/coreos-assembler/cosalib/cmdlib.py", line 362, in import_ostree_commit
        extract_image_json(workdir, commit)
        ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
      File "/usr/lib/coreos-assembler/cosalib/cmdlib.py", line 272, in extract_image_json
        raise Exception("Failed to extract image.json")
    Exception: Failed to extract image.json
    failed to execute cmd-osbuild: exit status 1
    ```
    
    Let's just have the caller explicitly tell us the path to the repo
    we want to import into is.

commit 776e5be50d3a092385251f17c2659ce35a535100
Author: Dusty Mabe <[email protected]>
Date:   Wed Sep 10 14:52:42 2025 -0400

    cmd-import: generate the oci manifest from ociarchive
    
    Operate on the ociarchive directly rather than args.srcimg because
    otherwise the manifest we fetch with skopeo *could* be a manifest list.
    
    Fixes #4310

[gemini-code-assist]

Code Review

This pull request introduces a series of cleanups and fixes for the container-based build process. The changes are well-motivated and improve the robustness and maintainability of the build scripts.

Key improvements include:

• Fixing how the NAME variable is sourced from argument files to handle non-standard bash syntax.
• Cleaning up override repository metadata more reliably to prevent build errors.
• Removing a hardcoded repository path in import_oci_archive by passing it as an argument, which resolves an issue with transient tmp/ directories.
• Generating the OCI manifest from the ociarchive directly to correctly handle manifest lists.

My review includes one suggestion for src/cmd-build-with-buildah to use a more robust method for checking file existence. Overall, these are solid improvements.

[dustymabe]

PR was previously approved and I applied the code review comment. Merging.