go/workspace: implement EvalHscloudNix

This allows us to access hscloud nix 'facts' from Go.

Change-Id: Ic8fc3350a7d073947c44529fcae0bbb8627421aa
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1508
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/BUILD b/BUILD
index d530075..fe75de7 100644
--- a/BUILD
+++ b/BUILD
@@ -1,6 +1,9 @@
 # Gazelle settings
 load("@bazel_gazelle//:def.bzl", "gazelle")
 
+# Used by //go/workspace tests.
+exports_files(["WORKSPACE", "default.nix"])
+
 # gazelle:prefix code.hackerspace.pl/hscloud
 # gazelle:go_naming_convention go_default_library
 gazelle(