mdadm4: init at 4.0

Would be just mdadm: 3.3.4 -> 4.0, but it doesn't look like there are
urgent bugfixes, and it is a major release, and wrong RAID handling
kills data, so let's let the early adopters test it a bit.

pkgs/os-specific/linux/mdadm/4.nix

@@ -0,0 +1,42 @@
+{ stdenv, fetchurl, groff }:
+
+assert stdenv.isLinux;
+
+stdenv.mkDerivation rec {
+  name = "mdadm-4.0";
+
+  src = fetchurl {
+    url = "mirror://kernel/linux/utils/raid/mdadm/${name}.tar.xz";
+    sha256 = "1ad3mma641946wn5lsllwf0lifw9lps34fv1nnkhyfpd9krffshx";
+  };
+
+  # This is to avoid self-references, which causes the initrd to explode
+  # in size and in turn prevents mdraid systems from booting.
+  allowedReferences = [ stdenv.glibc.out ];
+
+  patches = [ ./no-self-references.patch ];
+
+  makeFlags = [
+    "NIXOS=1" "INSTALL=install" "INSTALL_BINDIR=$(out)/sbin"
+    "MANDIR=$(out)/share/man" "RUN_DIR=/dev/.mdadm"
+  ] ++ stdenv.lib.optionals (stdenv ? cross) [
+    "CROSS_COMPILE=${stdenv.cross.config}-"
+  ];
+
+  nativeBuildInputs = [ groff ];
+
+  # Attempt removing if building with gcc5 when updating
+  NIX_CFLAGS_COMPILE = "-std=gnu89";
+
+  preConfigure = ''
+    sed -e 's@/lib/udev@''${out}/lib/udev@' \
+        -e 's@ -Werror @ @' \
+        -e 's@/usr/sbin/sendmail@/var/setuid-wrappers/sendmail@' -i Makefile
+  '';
+
+  meta = {
+    description = "Programs for managing RAID arrays under Linux";
+    homepage = http://neil.brown.name/blog/mdadm;
+    platforms = stdenv.lib.platforms.linux;
+  };
+}

pkgs/top-level/all-packages.nix

@@ -11496,6 +11496,7 @@ in
   mbpfan = callPackage ../os-specific/linux/mbpfan { };
 
   mdadm = callPackage ../os-specific/linux/mdadm { };
+  mdadm4 = callPackage ../os-specific/linux/mdadm/4.nix { };
 
   mingetty = callPackage ../os-specific/linux/mingetty { };