Add -Werror CI job

We should cause CLs that introduce compiler warnings to fail CI. Sadly
this will only cover Clang, but it will cover Clang for free, so it's
truly impossible to say if it's bad or not.

Change-Id: I45ca20d77251af9671d5cbe0d29cb08c5f1d03c2

1 files changed, 4 insertions, 0 deletions

diff --git a/flake.nix b/flake.nix
index 9a3087c4b..440320afa 100644
--- a/flake.nix
+++ b/flake.nix
@@ -283,6 +283,10 @@
               "address"
               "undefined"
             ];
+            # it is very hard to make *every* CI build use this option such
+            # that we don't wind up building Lix twice, so we do it here where
+            # we are already doing so.
+            werror = true;
           };
 
           # Make sure that nix-env still produces the exact same result