Fix size of time_t in vxworks

(backport <rust-lang#4268>)
(cherry picked from commit eec39f5)

Author: hax0kartik

src/vxworks/mod.rs

@@ -34,7 +34,7 @@ pub type ino_t = c_ulong;
 
 pub type rlim_t = c_ulong;
 pub type suseconds_t = c_long;
-pub type time_t = c_long;
+pub type time_t = c_longlong;
 
 pub type errno_t = c_int;