nixosTests.pantheon, nixosTests.budgie: Fail the test when coredump happens

[bobby285271]

Description of changes

Both tests succeed for me when a gsettings-desktop-schemas key removal crashes the desktop (see the GNOME 45 PR)

Make these tests fail like this when coredump happens:

subtest: Check if gala has ever coredumped
machine: must fail: coredumpctl --json=short | grep gala
Test "Check if gala has ever coredumped" failed with error: "command `coredumpctl --json=short | grep gala` unexpectedly succeeded"
cleanup
kill machine (pid 8)
machine # qemu-kvm: terminating on signal 15 from pid 6 (/nix/store/jhflvwr40xbb0xr6jx4311icp9cym1fp-python3-3.10.12/bin/python3.10)
(finished: cleanup, in 0.08 seconds)
kill vlan (pid 7)
error: builder for '/nix/store/5gmsbxdmnaxw72hcb6rw9nds8ik24p0n-vm-test-run-pantheon.drv' failed with exit code 1;

(These two desktops for now, I will look into other desktops I maintain later, still need to actually trigger some crash to verify the test)

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[bobby285271]

@ofborg test budgie pantheon

[bobby285271]

Since Pantheon can block the channel, I manually grepped dump in the recent hydra runs ¹ and don't aware of any coredumps.

Footnotes

1. https://hydra.nixos.org/job/nixos/trunk-combined/nixos.tests.pantheon.x86_64-linux and https://hydra.nixos.org/job/nixos/trunk-combined/nixos.tests.pantheon.aarch64-linux/ ↩