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the outdated pinned version we had in `./nixpkgs.nix`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>

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 { };
+    #lmbench = callPackage ./pkgs/lmbench/default.nix { }; # Broken
     mcxx = callPackage ./pkgs/mcxx/default.nix { };
     nanos6 = callPackage ./pkgs/nanos6/default.nix { };
     nanos6Debug = final.nanos6.override { enableDebug = true; };

pkgs/lmbench/default.nix

@@ -1,20 +1,19 @@
 {
   lib,
   stdenv,
-  libtirpc,
   fetchFromGitHub
 }:
 
 stdenv.mkDerivation rec {
   pname = "lmbench";
-  version = "941a0dcc";
+  version = "701c6c35";
 
   # We use the intel repo as they have fixed some problems
   src = fetchFromGitHub {
     owner = "intel";
     repo = pname;
-    rev = "941a0dcc0e7bdd9bb0dee05d7f620e77da8c43af";
-    sha256 = "sha256-SzwplRBO3V0R3m3p15n71ivYBMGoLsajFK2TapYxdqk=";
+    rev = "701c6c35b0270d4634fb1dc5272721340322b8ed";
+    sha256 = "0sf6zk03knkardsfd6qx7drpm56nhg53n885cylkggk83r38idyr";
   };
 
   postUnpack = ''
@@ -25,19 +24,12 @@ 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=$out
-      CPPFLAGS=-I${libtirpc.dev}/include/tirpc
-      LDFLAGS=-ltirpc
-    )
+    makeFlagsArray+=(BASE=$out)
   '';
 
   meta = {

pkgs/lmbench/fix-install.patch

@@ -1,10 +0,0 @@
---- 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