Make the bootsrap respect the contentAddressedByDefault setting

Patch every `derivation` call in the bootsrap process to add it a
conditional `__contentAddressed` parameter.

That way, passing `contentAddressedByDefault` means that the entire
build closure of a system can be content addressed

pkgs/stdenv/linux/default.nix

@@ -61,7 +61,16 @@ let
 
 
   # Download and unpack the bootstrap tools (coreutils, GCC, Glibc, ...).
-  bootstrapTools = import (if localSystem.libc == "musl" then ./bootstrap-tools-musl else ./bootstrap-tools) { inherit system bootstrapFiles; };
+  bootstrapTools = import (if localSystem.libc == "musl" then ./bootstrap-tools-musl else ./bootstrap-tools) {
+    inherit system bootstrapFiles;
+    extraAttrs = lib.optionalAttrs
+      (config.contentAddressedByDefault or false)
+      {
+        __contentAddressed = true;
+        outputHashAlgo = "sha256";
+        outputHashMode = "recursive";
+      };
+  };
 
   getLibc = stage: stage.${localSystem.libc};