Update PM gitlab URL to new server bscpm04.bsc.es

The old server has died, so we move to the new URL at bscpm04.bsc.es.

Reviewed-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Tested-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>

default.nix

@@ -1,19 +1,11 @@
 let
   bscOverlay = import ./overlay.nix;
 
-  # read flake.lock and determine revision from there
-  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
-  inherit (lock.nodes.nixpkgs.locked) rev narHash;
-  fetchedNixpkgs = builtins.fetchTarball {
-    url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
-    sha256 = narHash;
+  # Pin the nixpkgs
+  nixpkgsPath = import ./nixpkgs.nix;
+
+  pkgs = import nixpkgsPath {
+    overlays = [ bscOverlay ];
   };
-in
-{ overlays ? [ ]
-, nixpkgs ? fetchedNixpkgs
-, ...
-}@attrs:
-import nixpkgs (
-  (builtins.removeAttrs attrs [ "overlays" "nixpkgs" ]) //
-  { overlays = [ bscOverlay ] ++ overlays; }
-)
+
+in pkgs

flake.nix

@@ -13,9 +13,5 @@
       bscOverlay = import ./overlay.nix;
       overlays.default = self.bscOverlay;
       legacyPackages.x86_64-linux = pkgs;
-
-      hydraJobs = {
-        inherit (pkgs) bsc-ci;
-      };
     };
 }

nixpkgs.nix

@@ -0,0 +1,9 @@
+let
+  commit = "e4ad989506ec7d71f7302cc3067abd82730a4beb";
+in builtins.fetchTarball {
+    # Descriptive name to make the store path easier to identify
+    name = "nixpkgs-${commit}";
+    url = "https://github.com/nixos/nixpkgs/archive/${commit}.tar.gz";
+    # Hash obtained using `nix-prefetch-url --unpack <url>`
+    sha256 = "sha256-de9KYi8rSJpqvBfNwscWdalIJXPo8NjdIZcEJum1mH0=";
+}