check for db.sqlite rather than /nix/store

since we initialize the database last, it's safe to use the database as
a sentinel path

Author: Mic92

disko-install

@@ -253,7 +253,7 @@ main() {
   # nix copy uses up a lot of memory and we work around issues with incorrect checksums in our store
   # that can be caused by using closureInfo in combination with multiple builders and non-deterministic builds.
   # Therefore if we have a blank store, we copy the store paths and registration from the closureInfo.
-  if [[ ! -d "${mountPoint}/nix/store" ]]; then
+  if [[ ! -f "${mountPoint}/nix/var/nix/db/db.sqlite" ]]; then
     echo "Copying store paths" >&2
     mkdir -p "${mountPoint}/nix/store"
     xargs cp --recursive --target "${mountPoint}/nix/store"  < "${closure_info}/store-paths"

lib/make-disk-image.nix

@@ -93,7 +93,7 @@ let
 
     # We copy files with cp because `nix copy` seems to have a large memory leak
     mkdir -p ${systemToInstall.config.disko.rootMountPoint}/nix/store
-    xargs cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store < ${closureInfo}/store-paths
+    time xargs cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store < ${closureInfo}/store-paths
 
     ${systemToInstall.config.system.build.nixos-install}/bin/nixos-install --root ${systemToInstall.config.disko.rootMountPoint} --system ${systemToInstall.config.system.build.toplevel} --keep-going --no-channel-copy -v --no-root-password --option binary-caches ""
     umount -Rv ${systemToInstall.config.disko.rootMountPoint}