remove the assumption that game is ran from cwd at root

src/twn_engine_context_c.h

@@ -21,6 +21,8 @@ typedef struct EngineContext {
     /* the program's actual argc and argv */
     int argc;
     char **argv;
+    /* where the app was run from, used as the root for packs */
+    char *base_dir;
 
     /* configuration */
     toml_table_t *config_table;