Use nixpkgs from flake.lock and support attrs when importing bscpkgs

This makes `nix-build` and friends use the current flake lock instead of
the outdated pinned version we had in `./nixpkgs.nix`

With this, `nix-build -A ovni` and `nix build .#ovni` should produce the
same result.

This will fail if the flake nixpkgs input does not come from NixOS/nixpkgs.
We could use edolstra/flake-compat instead, but it's overkill imho.

Additionally, I made default.nix behave like nixpkgs, so that we can
import bscpkgs à la nixpkgs (Apply overlays and other options that nixpkgs
accepts):

```nix
let pkgs = import bscpkgs { inherit system; }; in <...>
```

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

default.nix

@@ -1,11 +1,19 @@
 let
   bscOverlay = import ./overlay.nix;
 
-  # Pin the nixpkgs
-  nixpkgsPath = import ./nixpkgs.nix;
-
-  pkgs = import nixpkgsPath {
-    overlays = [ bscOverlay ];
+  # 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;
   };
-
-in pkgs
+in
+{ overlays ? [ ]
+, nixpkgs ? fetchedNixpkgs
+, ...
+}@attrs:
+import nixpkgs (
+  (builtins.removeAttrs attrs [ "overlays" "nixpkgs" ]) //
+  { overlays = [ bscOverlay ] ++ overlays; }
+)

nixpkgs.nix

@@ -1,9 +0,0 @@
-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=";
-}

overlay.nix

@@ -21,7 +21,7 @@ let
     gpi-2 = callPackage ./pkgs/gpi-2/default.nix { };
     intelPackages_2023 = callPackage ./pkgs/intel-oneapi/2023.nix { };
     jemallocNanos6 = callPackage ./pkgs/nanos6/jemalloc.nix { };
-    #lmbench = callPackage ./pkgs/lmbench/default.nix { }; # Broken
+    lmbench = callPackage ./pkgs/lmbench/default.nix { };
     mcxx = callPackage ./pkgs/mcxx/default.nix { };
     nanos6 = callPackage ./pkgs/nanos6/default.nix { };
     nanos6Debug = final.nanos6.override { enableDebug = true; };

pkgs/lmbench/default.nix

@@ -1,19 +1,20 @@
 {
   lib,
   stdenv,
+  libtirpc,
   fetchFromGitHub
 }:
 
 stdenv.mkDerivation rec {
   pname = "lmbench";
-  version = "701c6c35";
+  version = "941a0dcc";
 
   # We use the intel repo as they have fixed some problems
   src = fetchFromGitHub {
     owner = "intel";
     repo = pname;
-    rev = "701c6c35b0270d4634fb1dc5272721340322b8ed";
-    sha256 = "0sf6zk03knkardsfd6qx7drpm56nhg53n885cylkggk83r38idyr";
+    rev = "941a0dcc0e7bdd9bb0dee05d7f620e77da8c43af";
+    sha256 = "sha256-SzwplRBO3V0R3m3p15n71ivYBMGoLsajFK2TapYxdqk=";
   };
 
   postUnpack = ''
@@ -24,12 +25,19 @@ stdenv.mkDerivation rec {
     sed -i "s@/bin/rm@rm@g" $(find . -name Makefile)
   '';
 
+  buildInputs = [ libtirpc ];
+  patches = [ ./fix-install.patch ];
+
   hardeningDisable = [ "all" ];
 
   enableParallelBuilding = false;
 
   preBuild = ''
-    makeFlagsArray+=(BASE=$out)
+    makeFlagsArray+=(
+      BASE=$out
+      CPPFLAGS=-I${libtirpc.dev}/include/tirpc
+      LDFLAGS=-ltirpc
+    )
   '';
 
   meta = {

pkgs/lmbench/fix-install.patch

@@ -0,0 +1,10 @@
+--- a/Makefile
++++ b/Makefile
+@@ -144,6 +144,7 @@ install-target:
+ 	if [ ! -d $(BASE)/include ]; then mkdir $(BASE)/include; fi
+ 	if [ ! -d $(BASE)/lib ]; then mkdir $(BASE)/lib; fi
+ 	cp $(EXES) $(BASE)/bin
++	cp $(OPT_EXES) $(BASE)/bin
+ 	cp $(INCS) $(BASE)/include
+ 	cp $O/lmbench.a $(BASE)/lib/libmbench.a
+ 	cd ../doc; env MAKEFLAGS="$(MAKEFLAGS)" make CC="${CC}" OS="${OS}" BASE="$(BASE)" install