mkosi: Use F40 tools tree in CI

Arch doesn't build:

No VM guests are running outdated hypervisor (qemu) binaries on this host.
/usr/bin/pacman-key: line 31: /usr/share/makepkg/util/message.sh: No such file or directory
/usr/bin/pacman-key: line 32: /usr/share/makepkg/util/parseopts.sh: No such file or directory
/usr/bin/pacman-key: line 620: parseopts: command not found

Author: daandemeyer

.github/workflows/mkosi.yml

@@ -100,6 +100,11 @@ jobs:
         # Sometimes we run on a host with /dev/kvm, but it is broken, so explicitly disable it
         QemuKvm=no
         Ephemeral=yes
+
+        [Build]
+        ToolsTree=default
+        ToolsTreeDistribution=fedora
+        ToolsTreeRelease=40
         EOF
 
         # For erofs, we have to install linux-modules-extra-azure, but that doesn't match the running kernel