pkgsStatic.ruff: ignore tests

doctests do not appear to respect the linker option set in
`.cargo/config.toml`.

Until this gets fixed, tests are disabled on static builds.

error:
```
---- crates/red_knot_python_semantic/src/module_name.rs - module_name::ModuleName::parent (line 84) stdout ----
error: linker `cc` not found
  |
  = note: No such file or directory (os error 2)

error: aborting due to 1 previous error

Couldn't compile the test.
```

pkgs/by-name/ru/ruff/package.nix

@@ -71,7 +71,10 @@ python3Packages.buildPythonPackage rec {
 
   # Run cargo tests
   cargoCheckType = "debug";
-  postInstallCheck = ''
+  # tests do not appear to respect linker options on doctests
+  # Upstream issue: https://github.com/rust-lang/cargo/issues/14189
+  # This causes errors like "error: linker `cc` not found" on static builds
+  postInstallCheck = lib.optionalString (!stdenv.hostPlatform.isStatic) ''
     cargoCheckHook
   '';