fix: allow using virtiofs share as writable /nix/store overlay

Author: songpola

nixos-modules/microvm/mounts.nix

@@ -82,6 +82,7 @@ lib.mkIf config.microvm.guest.enable {
           "lowerdir=${roStore}"
           "upperdir=${writableStoreOverlay}/store"
           "workdir=${writableStoreOverlay}/work"
+          "userxattr" # FIXME: only when writableStoreOverlay is a virtiofs share
         ];
         depends = [ roStore writableStoreOverlay ];
       };
@@ -136,6 +137,7 @@ lib.mkIf config.microvm.guest.enable {
         "lowerdir=/sysroot${roStore}"
         "upperdir=/sysroot${writableStoreOverlay}/store"
         "workdir=/sysroot${writableStoreOverlay}/work"
+        "userxattr" # FIXME: only when writableStoreOverlay is a virtiofs share
       ];
       wantedBy = [ "initrd-fs.target" ];
       before = [ "initrd-fs.target" ];