out_stackdriver: use new 'pthread' wrapper
#include <fluent-bit/flb_time.h>
#include <fluent-bit/flb_oauth2.h>
#include <fluent-bit/flb_regex.h>
+#include <fluent-bit/flb_pthread.h>
#include <msgpack.h>
#include "stackdriver_helper.h"
#include <mbedtls/base64.h>
#include <mbedtls/sha256.h>
-#include <pthread.h>
/*
* Base64 Encoding in JWT must:
