Set os.platform as hurd on GNU/Hurd

This makes it possible to detect quickjs is running on GNU/Hurd.

Author: pinotree

quickjs-libc.c

@@ -4029,6 +4029,8 @@ void js_std_set_worker_new_context_func(JSContext *(*func)(JSRuntime *rt))
 #define OS_PLATFORM "freebsd"
 #elif defined(__wasi__)
 #define OS_PLATFORM "wasi"
+#elif defined(__GNU__)
+#define OS_PLATFORM "hurd"
 #else
 #define OS_PLATFORM "unknown"
 #endif