flake: fix nix flake check --all-systems --no-build again (#395520)

.github/workflows/eval.yml

@@ -75,6 +75,9 @@ jobs:
         with:
           extra_nix_config: sandbox = true
 
+      - name: Ensure flake outputs on all systems still evaluate
+        run: nix --experimental-features 'nix-command flakes' flake check --all-systems --no-build
+
       - name: Query nixpkgs with aliases enabled to check for basic syntax errors
         run: |
           time nix-env -I ./nixpkgs -f ./nixpkgs -qa '*' --option restrict-eval true --option allow-import-from-derivation false >/dev/null

flake.nix

@@ -107,6 +107,10 @@
               self.legacyPackages.${system}.stdenv.hostPlatform.isLinux
               # Exclude power64 due to "libressl is not available on the requested hostPlatform" with hostPlatform being power64
               && !self.legacyPackages.${system}.targetPlatform.isPower64
+              # Exclude armv6l-linux because "cannot bootstrap GHC on this platform ('armv6l-linux' with libc 'defaultLibc')"
+              && system != "armv6l-linux"
+              # Exclude riscv64-linux because "cannot bootstrap GHC on this platform ('riscv64-linux' with libc 'defaultLibc')"
+              && system != "riscv64-linux"
             )
             {
               # Test that ensures that the nixosSystem function can accept a lib argument