Enable separate debug info

You can now pass

  separateDebugInfo = true;

to mkDerivation. This causes debug info to be separated from ELF
binaries and stored in the "debug" output. The advantage is that it
enables installing lean binaries, while still having the ability to
make sense of core dumps, etc.

pkgs/tools/package-management/nix/default.nix

@@ -41,7 +41,9 @@ let
 
     installFlags = "sysconfdir=$(out)/etc";
 
-    doInstallCheck = true;
+    doInstallCheck = false;
+
+    separateDebugInfo = true;
 
     crossAttrs = {
       postUnpack =