core: Include winpthreads.h on Windows
On Windows, we need to include the emulation header file in order
to use pthread functions. Fix it.
#include <fluent-bit/flb_info.h>
+#ifdef FLB_SYSTEM_WINDOWS
+#include <monkey/mk_core/external/winpthreads.h>
+#endif
+
/* Ideal case when the compiler support direct storage through __thread */
#ifdef FLB_HAVE_C_TLS
#define FLB_TLS_SET(key, val) key=val
