manual-config: Put `source' before the version in the sourceRoot name

nix's version parsing treats the previous name as a package named
`linux' with version `${version}-source', when we really want a package
named `linux-source' with version `${version}'

Signed-off-by: Shea Levy <shea@shealevy.com>

pkgs/os-specific/linux/kernel/manual-config.nix

@@ -67,7 +67,7 @@ let
   installTarget = target: [ (if target == "uImage" then "uinstall" else "install") ];
 
   sourceRoot = stdenv.mkDerivation {
-    name = "linux-${version}-source";
+    name = "linux-source-${version}";
 
     inherit src;