fix(package): nix-derivation-hash: purify

package/nix-derivation-hash/default.nix

@@ -1,9 +1,13 @@
 {
   writeShellScriptBin,
   bash,
+  nix,
 }: let
   # Use folder name as name of this system
   name = builtins.baseNameOf ./.;
 in writeShellScriptBin name /* sh */ ''
+  set -a
+  BIN_NIX_HASH="${nix}/bin/nix-hash"
+  set +a
   ${bash}/bin/sh ${./${name}.sh} "$@"
 ''

package/nix-derivation-hash/nix-derivation-hash.sh

@@ -1,9 +1,9 @@
 path="$1"
 base_path_name="$(basename "$path")"
-sha256="$(nix-hash --type sha256 "$path")"
+sha256="$("$BIN_NIX_HASH" --type sha256 "$path")"
 temp_dir="$(mktemp -d)"
 temp_file="${temp_dir}/${base_path_name}.str"
 printf "source:sha256:%s:/nix/store:%s" "$sha256" "$base_path_name" > "$temp_file"
-nix-hash --type sha256 --truncate --base32 --flat "$temp_file"
+"$BIN_NIX_HASH" --type sha256 --truncate --base32 --flat "$temp_file"
 
 rm -rf "${temp_dir:?}"