Add my custom packages

Something easier than setting my own NUR, at least.

pkgs/default.nix

@@ -0,0 +1,5 @@
+{ pkgs ? <nixpkgs> }:
+
+{
+  libcs50 = pkgs.callPackage ./libcs50.nix { };
+}

pkgs/libcs50.nix

@@ -0,0 +1,28 @@
+{ stdenv, lib, fetchFromGitHub, gnused }:
+
+stdenv.mkDerivation rec {
+  pname = "libcs50";
+  version = "10.1.1";
+
+  src = fetchFromGitHub {
+    owner = "cs50";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "sha256:0ckbhm3287yva94zqls8wi06bwk5f5386h5g1wz8jrlzwxw1s4ib";
+  };
+
+  makeFlags = [ "DESTDIR=$(out)" ];
+
+  configurePhase = ''
+    # Don't use ldconfig.
+    ${gnused}/bin/sed -i -e '60,62d' Makefile
+  '';
+
+  meta = with lib; {
+    homepage = "https://github.com/cs50/libcs50";
+    description = "CS50 C library used for the problem sets";
+    license = licenses.mit;
+    platforms = platforms.all;
+  };
+}
+