home-manager: handle args with spaces to doBuildAttr
home-manager: handle args with spaces to doBuildAttr

Presently, if you pass an argument with spaces in it to `doBuildAttr`,
it will be split it into multiple arguments to `nix build` or
`nix-build`. This situation arises, for example, on systems with
spaces in `XDG_DATA_HOME`.

Specifically, the `home-manager` script errors out in trying to
address the `read-news` state file. With this change, argument
separation should be preserved properly in `doBuildAttr`.

PR #1044

rycee/home-manager,rycee/home-manager,rycee/home-manager