linux/manual-config: put build and source trees into a separate 'dev' output.

This makes it possible to still build out-of-tree modules without making a system using this kernel depend on the full source and build tree at runtime.

Note that references to the source tree are removed from kernel modules after build.
Ideally, this would be accomplished by modifying the Makefile that puts the reference there in the first place, but I haven't tracked that down yet.

pkgs/os-specific/linux/kernel/manual-config.nix

@@ -75,16 +75,6 @@ let
     "INSTALL_PATH=$(out)"
   ] ++ (optional isModular "INSTALL_MOD_PATH=$(out)")
   ++ optional installsFirmware "INSTALL_FW_PATH=$(out)/lib/firmware";
-in
-
-stdenv.mkDerivation {
-  name = "linux-${version}";
-
-  enableParallelBuilding = true;
-
-  passthru = {
-    inherit version modDirVersion config kernelPatches src;
-  };
 
   sourceRoot = stdenv.mkDerivation {
     name = "linux-${version}-source";
@@ -108,11 +98,25 @@ stdenv.mkDerivation {
       mv $sourceRoot $out
     '';
   };
+in
+
+stdenv.mkDerivation {
+  name = "linux-${version}";
+
+  enableParallelBuilding = true;
+
+  outputs = if isModular then [ "out" "dev" ] else null;
+
+  passthru = {
+    inherit version modDirVersion config kernelPatches src;
+  };
+
+  inherit sourceRoot;
 
   unpackPhase = ''
     mkdir build
     export buildRoot="$(pwd)/build"
-    cd $sourceRoot
+    cd ${sourceRoot}
   '';
 
   configurePhase = ''
@@ -140,7 +144,9 @@ stdenv.mkDerivation {
     make modules_install $makeFlags "''${makeFlagsArray[@]}" \
       $installFlags "''${installFlagsArray[@]}"
     rm -f $out/lib/modules/${modDirVersion}/build
-    mv $buildRoot $out/lib/modules/${modDirVersion}/build
+    mkdir -p $dev/lib/modules/${modDirVersion}
+    mv $out/lib/modules/${modDirVersion}/source $dev/lib/modules/${modDirVersion}/source
+    mv $buildRoot $dev/lib/modules/${modDirVersion}/build
   '' else optionalString installsFirmware ''
     make firmware_install $makeFlags "''${makeFlagsArray[@]}" \
       $installFlags "''${installFlagsArray[@]}"
@@ -149,6 +155,10 @@ stdenv.mkDerivation {
   postFixup = if isModular then ''
     if [ -z "$dontStrip" ]; then
         find $out -name "*.ko" -print0 | xargs -0 -r strip -S
+        # Remove all references to the source directory to avoid unneeded
+        # runtime dependencies
+        find $out -name "*.ko" -print0 | xargs -0 -r sed -i \
+          "s|${sourceRoot}|$NIX_STORE/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${sourceRoot.name}|g"
     fi
   '' else null;
 

pkgs/top-level/all-packages.nix

@@ -6013,7 +6013,7 @@ let
       callPackage = newScope self; 
 
       self = {
-        inherit kernel;
+        kernel = kernel.dev or kernel;
 
         acpi_call = callPackage ../os-specific/linux/acpi-call {};
 
@@ -6115,7 +6115,7 @@ let
 
         zfs = callPackage ../os-specific/linux/zfs/default.nix { };
       };
-    in self;
+    in (self // { kernel = self.kernel.out; });
 
   # Build the kernel modules for the some of the kernels.
   linuxPackages_2_6_32 = recurseIntoAttrs (linuxPackagesFor linux_2_6_32);