clan-vm-manager: devshell doesn't require clan-cli derivation

pkgs/clan-cli/.envrc

@@ -1,7 +1,7 @@
 # BUG: If this is enabled the devshell depends on clan_cli building successfully
 # source_up
 
-watch_file flake-module.nix default.nix
+watch_file flake-module.nix shell.nix default.nix
 
 # Because we depend on nixpkgs sources, uploading to builders takes a long time
 use flake .#clan-cli --builders ''

pkgs/clan-cli/shell.nix

@@ -24,6 +24,7 @@ mkShell {
   shellHook = ''
     export PATH=$(pwd)/bin:$PATH
 
+    # Needed for impure tests
     ln -sfT ${clan-cli.nixpkgs} clan_cli/nixpkgs
   '';
 }