mkosi: Use zstd compression on non-centos distros

Just because centos doesn't support it doesn't mean we can't use it
on the other distros.

mkosi.presets/10-initrd/mkosi.conf

@@ -5,11 +5,9 @@ Bootable=auto,yes
 
 [Output]
 Format=cpio
-# TODO: Switch to zstd once we stop building CentOS Stream 8.
-CompressOutput=xz
 
 [Content]
-BaseTrees=mkosi.output/base
+BaseTrees=../../mkosi.output/base
 MakeInitrd=yes
 
 # Arch Linux doesn't split their gcc-libs package so we manually remove unneeded stuff here to make sure it

mkosi.presets/10-initrd/mkosi.conf.d/10-centos.conf

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+[Match]
+Distribution=centos
+
+[Output]
+# TODO: Switch to zstd once we stop building CentOS Stream 8.
+CompressOutput=xz

mkosi.presets/10-initrd/mkosi.conf.d/10-default.conf

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+[Match]
+Distribution=arch debian fedora opensuse ubuntu
+
+[Output]
+CompressOutput=zst