solaris: fix compile error on ctime_r()

On Solaris, it takes a 3rd length argument.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/os/os.h b/os/os.h
index 8d2a6ae..c6da0c3 100644
--- a/os/os.h
+++ b/os/os.h
@@ -142,6 +142,10 @@
 typedef socklen_t fio_socklen_t;
 #endif
 
+#ifndef FIO_OS_HAS_CTIME_R
+#define os_ctime_r(x, y, z)     ctime_r((x), (y))
+#endif
+
 #ifdef FIO_USE_GENERIC_SWAP
 static inline uint16_t fio_swap16(uint16_t val)
 {