Allow relative paths in flakerefs

Also allow "." as an installable to refer to the flake in the current
directory. E.g.

  $ nix build .

will build 'provides.defaultPackage' in the flake in the current
directory.

1 files changed, 1 insertions, 0 deletions

diff --git a/flake.nix b/flake.nix
index b119f0324..695f67fa4 100644
--- a/flake.nix
+++ b/flake.nix
@@ -14,5 +14,6 @@
 
     packages.nix = hydraJobs.build.x86_64-linux;
 
+    defaultPackage = packages.nix;
   };
 }