Installation issue: `font-util` is not sandboxed

[tpadioleau]

Steps to reproduce the issue

1. Install the following sandboxed environment:

spack:
  concretizer:
    reuse: false
    unify: true
  config:
    sandbox:
      enable: true
      allow_network: false
      allow_read:
        - /
  packages:
    all:
      require:
        - 'target=x86_64'
  repos:
    builtin:
      tag: v2026.06.0
  specs:
    - 'font-util'

Error message

Error message

  /local/home/tpadiole/spack-1.2.1/opt/spack/linux-x86_64/font-util-1.4.1-lp4hilvo5l5jap5hlnw3qdnty572se2s/share/fonts/X11/100dpi: failed to write cache
> /local/home/tpadiole/.cache/fontconfig/05daf39db643a234fa5868630e8f2c02-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/dc64efbc58b4f8e6c0a03d870cfb09e0-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/044198e785e1bc32a6aeaf120cba01a8-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/3a80303c95f2c5a9a58415c715cdf260-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/b1b869960efc787df50f54ff3ff97e44-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/5854c9a30d9b7221faecd0634ea58164-le64.cache-9: Permission denied
> /local/home/tpadiole/.cache/fontconfig/55bd518c358553a84d11ab6523e4a21f-le64.cache-9: Permission denied
> make[2]: *** [Makefile:900: install-data-hook] Error 1
  make[2]: Leaving directory '/tmp/tpadiole/spack-stage/spack-stage-font-util-1.4.1-lp4hilvo5l5jap5hlnw3qdnty572se2s/spack-src/font-adobe-100dpi/font-adobe-100dpi-1.0.3'
> make[1]: *** [Makefile:788: install-data-am] Error 2
  make[1]: Leaving directory '/tmp/tpadiole/spack-stage/spack-stage-font-util-1.4.1-lp4hilvo5l5jap5hlnw3qdnty572se2s/spack-src/font-adobe-100dpi/font-adobe-100dpi-1.0.3'
> make: *** [Makefile:739: install-am] Error 2
  Traceback (most recent call last):
    File "/local/home/tpadiole/spack-1.2.1/lib/spack/spack/builder.py", line 298, in _wrapped
      return fn(builder.pkg_with_dispatcher)
    File "/local/home/tpadiole/.spack/package_repos/fncqgg4/repos/spack_repo/builtin/packages/font_util/package.py", line 263, in font_install
      make("install")
      ~~~~^^^^^^^^^^^
-- lines 3479 to 3485 --
    File "/local/home/tpadiole/spack-1.2.1/lib/spack/spack/new_installer.py", line 371, in _mkdtemp
      return tempfile.mkdtemp(dir=dir, prefix=prefix, suffix=suffix)
             ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/usr/lib/python3.14/tempfile.py", line 381, in mkdtemp
      _os.mkdir(file, 0o700)
      ~~~~~~~~~^^^^^^^^^^^^^
> PermissionError: [Errno 13] Permission denied: '/local/home/tpadiole/spack-1.2.1/opt/spack/linux-x86_64/.3b9q4sh1.garbage'
==> Updating view at /local/home/tpadiole/spack-1.2.1/var/spack/environments/test/.spack-env/view
==> Error: The following packages failed to install:
font-util@1.4.1/lp4hilvo5l5jap5hlnw3qdnty572se2s: /tmp/tpadiole/spack-stage/spack-stage-font-util-1.4.1-lp4hilvo5l5jap5hlnw3qdnty572se2s-gsyulse3.log

Information on your system

• Spack: 1.2.1
• Builtin repo: d4f7c71
• Python: 3.14.4
• Platform: linux-ubuntu26.04-icelake

Additional information

spack-build-env.txt

spack-build-out.txt

General information

• I have run spack debug report and reported the version of Spack/Python/Platform
• I have run spack maintainers <name-of-the-package> and @mentioned any maintainers
• I have uploaded the build log and environment files
• I have searched the issues of this repo and believe this is not a duplicate