Ignore expansion test if cargo-expand subcommand isn't present

test_suite/tests/expandtest.rs

@@ -1,5 +1,6 @@
 #[cfg(not(target_os = "emscripten"))]
 #[rustversion::attr(not(nightly), ignore)]
+#[cfg_attr(not(cargo_expand), ignore)]
 #[test]
 fn expandtest() {
     macrotest::expand("tests/expand/**/enum/*.rs");