xen: use SeaBIOS' passthru.firmware attribute

[SigmaSquadron]

Description of changes

• Makes the generic Xen builder use firmware instead of hard-coding a directory path.
  • This is useful for when seabios is overridden by qubes-seabios in qubes-vmm-xen (qubes-vmm-xen: init at 4.19.0-5, qubes-seabios: init at 4.0.2 #341429).

Requires #342692
Closes #345172

Things done

• Built on platform(s)
  • x86_64-linux
• 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 pr 345324". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[AndersonTorres]

By reading the Makefile from SeaBIOS project I found this:

https://github.com/coreboot/seabios/blob/2424e4c04aa30d90e85073ea41d18a7845460783/Makefile#L98

target-y :=
target-$(CONFIG_QEMU) += $(OUT)bios.bin
target-$(CONFIG_CSM) += $(OUT)Csm16.bin
target-$(CONFIG_COREBOOT) += $(OUT)bios.bin.elf
target-$(CONFIG_BUILD_VGABIOS) += $(OUT)vgabios.bin

all: $(target-y)

In other words, it can build at least four different files, possibly at the same time.
So I think the better idea is to create split packages, one for each blob.
I will do it asap.

[SigmaSquadron]

I should note that this was partially superseded by #342692. I just haven't deleted the SeaBIOS commits yet.

[SigmaSquadron]

We should also probably change our SeaBIOS to seabios-qemu.

[SigmaSquadron]

Vagrant fails to build, but I'm not sure why; seems unrelated to Xen:

Running phase: installCheckPhase
Vagrant failed to initialize at a very early stage:

The plugins failed to initialize correctly. This may be due to manual
modifications made within the Vagrant home directory. Vagrant can
attempt to automatically correct this issue by running:

  vagrant plugin repair

If Vagrant was recently updated, this error may be due to incompatible
versions of dependencies. To fix this problem please remove and re-install
all plugins. Vagrant can attempt to do this automatically by running:

  vagrant plugin expunge --reinstall

Or you may want to try updating the installed plugins to their latest
versions:

  vagrant plugin update

Error message given during initialization: can't activate rexml-3.3.6, already activated rexml-3.2.5

cc @tylerjl

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nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 345324

---

x86_64-linux

⏩ 1 package marked as broken and skipped:

• qubes-core-vchan-xen

❌ 1 package failed to build:

• vagrant

✅ 57 packages built:

• appvm
• collectd
• diffoscope
• diffoscope.dist
• diffoscope.man
• docker-machine-kvm2
• gnome-boxes
• guestfs-tools
• htcondor
• libguestfs
• libguestfs-with-appliance
• librenms
• libvirt
• libvirt-glib
• libvirt-glib.dev
• libvirt-glib.devdoc
• libvmi
• libvmi.dev
• libvmi.lib
• mgmt
• minikube
• multipass
• ocamlPackages.ocaml_libvirt
• perl538Packages.SysVirt
• perl538Packages.SysVirt.devdoc
• perl540Packages.SysVirt
• perl540Packages.SysVirt.devdoc
• python311Packages.guestfs
• python311Packages.guestfs.dist
• python311Packages.libvirt
• python311Packages.libvirt.dist
• python311Packages.xen
• python311Packages.xen.boot
• python311Packages.xen.dev
• python311Packages.xen.doc
• python311Packages.xen.man
• python312Packages.guestfs
• python312Packages.guestfs.dist
• python312Packages.libvirt
• python312Packages.libvirt.dist
• xen (python312Packages.xen)
• xen.boot (python312Packages.xen.boot)
• xen.dev (python312Packages.xen.dev)
• xen.doc (python312Packages.xen.doc)
• xen.man (python312Packages.xen.man)
• qemu_xen
• qemu_xen.debug
• qemu_xen.ga
• rubyPackages.ruby-libvirt
• rubyPackages_3_1.ruby-libvirt
• rubyPackages_3_2.ruby-libvirt
• virt-manager
• virt-manager-qt
• virt-manager.dist
• virt-top
• virt-viewer
• xen-guest-agent