Have the kernel headers be a linuxPackage, use the current linuxPackage's headers

svn path=/nixpkgs/branches/stdenv-updates/; revision=29546

pkgs/os-specific/linux/kernel-headers/default.nix

@@ -0,0 +1,59 @@
+{stdenv, fetchurl, perl, cross ? null, kernel}:
+
+assert cross == null -> stdenv.isLinux;
+
+let
+  version = kernel.version;
+  kernelHeadersBaseConfig = if (cross == null) then
+      stdenv.platform.kernelHeadersBaseConfig
+    else
+      cross.platform.kernelHeadersBaseConfig;
+in
+
+stdenv.mkDerivation {
+  name = "linux-headers-${version}";
+
+  src = kernel.src;
+
+  targetConfig = if (cross != null) then cross.config else null;
+
+  platform =
+    if cross != null then cross.platform.kernelArch else
+    if stdenv.system == "i686-linux" then "i386" else
+    if stdenv.system == "x86_64-linux" then "x86_64" else
+    if stdenv.system == "powerpc-linux" then "powerpc" else
+    if stdenv.system == "armv5tel-linux" then "arm" else
+    if stdenv.platform ? kernelArch then stdenv.platform.kernelArch else
+    abort "don't know what the kernel include directory is called for this platform";
+
+  buildInputs = [perl];
+
+  extraIncludeDirs =
+    if cross != null then
+	(if cross.arch == "powerpc" then ["ppc"] else [])
+    else if stdenv.system == "powerpc-linux" then ["ppc"] else [];
+
+  buildPhase = ''
+    if test -n "$targetConfig"; then
+       export ARCH=$platform
+    fi
+    make ${kernelHeadersBaseConfig}
+    make mrproper headers_check
+  '';
+
+  installPhase = ''
+    make INSTALL_HDR_PATH=$out headers_install
+
+    # Some builds (e.g. KVM) want a kernel.release.
+    ensureDir $out/include/config
+    echo "${version}-default" > $out/include/config/kernel.release
+  '';
+
+  # !!! hacky
+  fixupPhase = ''
+    ln -s asm $out/include/asm-$platform
+    if test "$platform" = "i386" -o "$platform" = "x86_64"; then
+      ln -s asm $out/include/asm-x86
+    fi
+  '';
+}