nixos-anywhere: replace nix copy --derivation with nix flake archive

Author: Enzime

src/nixos-anywhere.sh

@@ -443,6 +443,12 @@ nixBuild() {
     "$@"
 }
 
+nixFlakeArchive() {
+  NIX_SSHOPTS="${sshArgs[*]}" nix flake archive \
+    "${nixOptions[@]}" \
+    "$@"
+}
+
 runVmTest() {
   if [[ -z ${flakeAttr} ]]; then
     echo "--vm-test is not supported with --store-paths" >&2
@@ -711,10 +717,7 @@ runDisko() {
     nixCopy --to "ssh://$sshConnection?$sshStoreSettings" "$diskoScript"
   elif [[ ${buildOn} == "remote" ]]; then
     step Building disko script
-    # We need to do a nix copy first because nix build doesn't have --no-check-sigs
-    # Use ssh:// here to avoid https://github.com/NixOS/nix/issues/7359
-    nixCopy --to "ssh://$sshConnection?$sshStoreSettings" "${flake}#${flakeAttr}.system.build.${diskoMode}Script" \
-      --derivation --no-check-sigs
+    nixFlakeArchive --to "ssh-ng://$sshConnection?ssh-key=$tempDir%2Fnixos-anywhere&$sshStoreSettings" "${flake}"
     # If we don't use ssh-ng here, we get `error: operation 'getFSAccessor' is not supported by store`
     diskoScript=$(
       nixBuild "${flake}#${flakeAttr}.system.build.${diskoAttr}" \
@@ -733,10 +736,7 @@ nixosInstall() {
     nixCopy --to "ssh://$sshConnection?remote-store=local%3Froot=%2Fmnt&$sshStoreSettings" "$nixosSystem"
   elif [[ ${buildOn} == "remote" ]]; then
     step Building the system closure
-    # We need to do a nix copy first because nix build doesn't have --no-check-sigs
-    # Use ssh:// here to avoid https://github.com/NixOS/nix/issues/7359
-    nixCopy --to "ssh://$sshConnection?remote-store=local%3Froot=%2Fmnt&$sshStoreSettings" "${flake}#${flakeAttr}.system.build.toplevel" \
-      --derivation --no-check-sigs
+    nixFlakeArchive --to "ssh-ng://$sshConnection?remote-store=local%3Froot=%2Fmnt&ssh-key=$tempDir%2Fnixos-anywhere&$sshStoreSettings" "${flake}"
     # If we don't use ssh-ng here, we get `error: operation 'getFSAccessor' is not supported by store`
     nixosSystem=$(
       nixBuild "${flake}#${flakeAttr}.system.build.toplevel" \