###### Motivation for this change
Update to latest upstream version
###### Things done
* [ ] Tested using sandboxing ([nix.useSandbox](http://nixos.org/nixos/manual/options.html#opt-nix.useSandbox) on NixOS, or option `sandbox` in [`nix.conf`](http://nixos.org/nix/manual/#sec-conf-file) on non-NixOS linux)
* Built on platform(s)
* [x] NixOS
* [ ] macOS
* [ ] other Linux distributions
* [ ] Tested via one or more NixOS test(s) if existing and applicable for the change (look inside [nixos/tests](https://github.com/NixOS/nixpkgs/blob/master/nixos/tests))
* [ ] Tested compilation of all pkgs that depend on this change using `nix-shell -p nix-review --run "nix-review wip"`
* [x] Tested execution of all binary files (usually in `./result/bin/`)
* [ ] Determined the impact on package closure size (by running `nix path-info -S` before and after)
* [ ] Ensured that relevant documentation is up to date
* [x] Fits [CONTRIBUTING.md](https://github.com/NixOS/nixpkgs/blob/master/.github/CONTRIBUTING.md).
Tested building qemu_kvm, qemu_full, and qemu_test on x86_64-linux.
Also tested booting a VM generated with nixos-rebuild build-vm.
I wasn't able to test building pkgsMusl.qemu_kvm, because of many
build failures in dependencies.
This allows us to continue to have the automatically sized image attempt
to build on Hydra, which should give us a good indication of when we've
got this fixed.
For reasons we haven't been able to work out, the aarch64 EC2 image now
regularly exceeds the output image size on hydra.nixos.org. As a
workaround, set this back to being statically sized again.
The other images do seem to build - it's just a case of the EC2 image
now being too large (occasionally non-determinstically).
This is supeer useful to allow the normal sd-image code to be used by
someone who wants to setup multiple partitions with a sd-image.
Currently I'm manually copying the sd-image file and modifying it
instead.
Guile's version is part of the path and the installed files won't be
found if we don't include it. Also, we can rely on the paths of build
inputs being added to $GUILE_LOAD_PATH and $GUILE_LOAD_COMPILED_PATH
by Guile's setup hook.
