cleanup 'str' API

src/arch_freertos.h

@@ -32,7 +32,7 @@
 #define calloc(a, b) mg_calloc(a, b)
 #define free(a) vPortFree(a)
 #define malloc(a) pvPortMalloc(a)
-#define strdup(s) ((char *) mg_strdup(mg_str(s)).buf)
+#define strdup(s) mg_mprintf("%s", s)
 
 // Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
 static inline void *mg_calloc(size_t cnt, size_t size) {