Fix arch eval error introduced in #61019

This occurs when using a `platform.gcc.arch` that isn't one of the
pre-existing hard-coded options.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/systems/architectures.nix b/lib/systems/architectures.nix
index 9d1c29fd9f0..bfecaec1ae8 100644
--- a/lib/systems/architectures.nix
+++ b/lib/systems/architectures.nix
@@ -60,7 +60,7 @@ rec {
   };
 
   predicates = let
-    featureSupport = feature: x: builtins.elem feature features.${x};
+    featureSupport = feature: x: builtins.elem feature features.${x} or [];
   in {
     sse3Support    = featureSupport "sse3";
     ssse3Support   = featureSupport "ssse3";