fix(ci): eval should fail if github-matrix run fails

Author: jfroche

.github/workflows/nix-eval.yml

@@ -30,5 +30,5 @@ jobs:
       - id: set-matrix
         name: Generate Nix Matrix
         run: |
-          set -Eeu
-          echo matrix="$(nix run --accept-flake-config .\#github-matrix checks legacyPackages)" >> "$GITHUB_OUTPUT"
+          set -Eeu -o pipefail
+          echo matrix="$(nix run --accept-flake-config .\#github-matrix -- checks legacyPackages)" >> "$GITHUB_OUTPUT"