make-disk-image: create directories images in out path

In case we are crossing some filesystem boundary (i.e. /tmp -> /nix/store),
this is faster. Also tmpfs might be probelemantic regarding memory usage.

Author: Mic92

lib/make-disk-image.nix

@@ -54,16 +54,15 @@ let
     xcp'
   ] ++ cfg.extraDependencies;
   preVM = ''
-    ${lib.concatMapStringsSep "\n" (disk: "${pkgs.qemu}/bin/qemu-img create -f ${imageFormat} ${disk.imageName}.${imageFormat} ${disk.imageSize}") (lib.attrValues diskoCfg.devices.disk)}
+    mkdir -p "$out"
+    ${lib.concatMapStringsSep "\n" (disk: "${pkgs.qemu}/bin/qemu-img create -f ${imageFormat} \"$out/${disk.imageName}.${imageFormat}\" ${disk.imageSize}") (lib.attrValues diskoCfg.devices.disk)}
     # This makes disko work, when canTouchEfiVariables is set to true.
     # Technically these boot entries will no be persisted this way, but
     # in most cases this is OK, because we can rely on the standard location for UEFI executables.
     install -m600 ${pkgs.OVMF.variables} efivars.fd
   '';
   postVM = ''
     # shellcheck disable=SC2154
-    mkdir -p "$out"
-    ${lib.concatMapStringsSep "\n" (disk: "mv ${disk.imageName}.${imageFormat} \"$out\"/${disk.imageName}.${imageFormat}") (lib.attrValues diskoCfg.devices.disk)}
     ${cfg.extraPostVM}
   '';
 
@@ -111,7 +110,7 @@ let
     "-drive if=pflash,format=raw,unit=1,file=efivars.fd"
   ] ++ builtins.map
     (disk:
-      "-drive file=${disk.imageName}.${imageFormat},if=virtio,cache=unsafe,werror=report,format=${imageFormat}"
+      "-drive file=\"$out\"/${disk.imageName}.${imageFormat},if=virtio,cache=unsafe,werror=report,format=${imageFormat}"
     )
     (lib.attrValues diskoCfg.devices.disk));
 in