nixguix: Add unsupported file extensions configuration list

Related to D3745

Test Plan

bin/octocatalog on staging node:

$ bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details --to staging worker0.internal.staging.swh.network
Found host worker0.internal.staging.swh.network
Cloning into '/tmp/swh-ocd.glkkMJNO/environments/production/data/private'...
done.
Cloning into '/tmp/swh-ocd.glkkMJNO/environments/staging/data/private'...
done.
*** Running octocatalog-diff on host worker0.internal.staging.swh.network
I, [2020-08-08T13:18:57.332561 #9375]  INFO -- : Catalogs compiled for worker0.internal.staging.swh.network
I, [2020-08-08T13:18:58.322812 #9375]  INFO -- : Diffs computed for worker0.internal.staging.swh.network
diff origin/production/worker0.internal.staging.swh.network current/worker0.internal.staging.swh.network
*******************************************
  File[/etc/softwareheritage/loader_nixguix.yml] =>
   parameters =>
     content =>
      @@ -20,3 +20,19 @@
         task_queues:
         - swh.loader.package.nixguix.tasks.LoadNixguix
      +unsupported_file_extensions:
      +- patch
      +- iso
      +- whl
      +- gem
      +- pom
      +- msi
      +- pod
      +- png
      +- rock
      +- ttf
      +- jar
      +- c
      +- el
      +- rpm
      +- diff
      _
*******************************************
*** End octocatalog-diff on worker0.internal.staging.swh.network

---

Migrated from D3747 (view on Phabricator)