build-support/vm: refactor IFS tricks in fillDiskWithDebs

            memSize

            ;

          # Flatten this into string explicitly to allow IFS tricks below to work,

          # and support structuredAttrs

          debsInterspersed = toString (lib.intersperse "|" debs);

          debsFlat = lib.flatten debs;

          debsGrouped = debs;

          preVM = createEmptyImage { inherit size fullName; };

            # (which have lots of circular dependencies) from barfing.

            echo "unpacking Debs..."

            for deb in $debsInterspersed; do

              if test "$deb" != "|"; then

            for deb in "''${debsFlat[@]}"; do

              echo "$deb..."

              dpkg-deb --extract "$deb" /mnt

              fi

            done

            # Make the Nix store available in /mnt, because that's where the .debs live.

            export DEBIAN_FRONTEND=noninteractive

            oldIFS="$IFS"

            IFS="|"

            for component in $debsInterspersed; do

              IFS="$oldIFS"

            for component in "''${debsGrouped[@]}"; do

              echo

              echo ">>> INSTALLING COMPONENT: $component"

              debs=