Cache config as a file

wasmtime-environ/tests/cache_default_config_in_memory.rs

@@ -0,0 +1,7 @@
+use wasmtime_environ::cache_config;
+
+#[test]
+fn test_cache_default_config_in_memory() {
+    let errors = cache_config::init::<&str>(true, None, false);
+    assert!(errors.is_empty());
+}