Update process vxworks, stack size set to libc::PTHREAD_STACK_MIN and remove thread::min_stack() reference

Author: B I Mohammed Abbas

library/std/src/sys/pal/unix/process/process_vxworks.rs

@@ -4,7 +4,6 @@ use crate::num::NonZero;
 use crate::sys;
 use crate::sys::cvt;
 use crate::sys::process::process_common::*;
-use crate::sys_common::thread;
 use libc::RTP_ID;
 use libc::{self, c_char, c_int};
 
@@ -68,7 +67,7 @@ impl Command {
                 .as_ref()
                 .map(|c| c.as_ptr())
                 .unwrap_or_else(|| *sys::os::environ() as *const _);
-            let stack_size = thread::min_stack();
+            let stack_size = libc::PTHREAD_STACK_MIN;
 
             // ensure that access to the environment is synchronized
             let _lock = sys::os::env_read_lock();