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/bootstrap-tools/default.nix

@@ -1,6 +1,6 @@
-{ system, bootstrapFiles }:
+{ system, bootstrapFiles, extraAttrs }:
 
-derivation {
+derivation ({
   name = "bootstrap-tools";
 
   builder = bootstrapFiles.busybox;
@@ -15,4 +15,4 @@ derivation {
   langC = true;
   langCC = true;
   isGNU = true;
-}
+} // extraAttrs)