Fix sigaction.sa_flags type: c_int -> c_ulong

nix 0.30.1 expects SaFlags_t = c_ulong for target_os = "redox"
(see nix-0.30.1/src/sys/signal.rs:430). Our relibc had c_int,
causing type mismatch errors in uutils and any nix-dependent crate.
Align with nix's expectation.

src/header/signal/mod.rs

@@ -12,7 +12,7 @@ use crate::{
     platform::{
         self, ERRNO, Pal, PalSignal, Sys,
         types::{
-            c_char, c_int, c_ulonglong, c_void, pid_t, pthread_attr_t, pthread_t, size_t, uid_t,
+            c_char, c_int, c_ulong, c_ulonglong, c_void, pid_t, pthread_attr_t, pthread_t, size_t, uid_t,
         },
     },
 };
@@ -56,7 +56,7 @@ pub const SIGEV_THREAD: c_int = 2;
 /// cbindgen:ignore
 pub struct sigaction {
     pub sa_handler: Option<extern "C" fn(c_int)>,
-    pub sa_flags: c_int,
+    pub sa_flags: c_ulong,
     pub sa_restorer: Option<unsafe extern "C" fn()>,
     pub sa_mask: sigset_t,
 }
@@ -300,9 +300,9 @@ pub extern "C" fn siginterrupt(sig: c_int, flag: c_int) -> c_int {
     unsafe { sigaction(sig, ptr::null_mut(), psa.as_mut_ptr()) };
     let mut sa = unsafe { psa.assume_init() };
     if flag != 0 {
-        sa.sa_flags &= !SA_RESTART as c_int;
+        sa.sa_flags &= !SA_RESTART as c_ulong;
     } else {
-        sa.sa_flags |= SA_RESTART as c_int;
+        sa.sa_flags |= SA_RESTART as c_ulong;
     }
 
     unsafe { sigaction(sig, &raw const sa, ptr::null_mut()) }
@@ -457,7 +457,7 @@ pub unsafe extern "C" fn sigset(
         } else {
             let mut sa = sigaction {
                 sa_handler: func,
-                sa_flags: c_int::from(0),
+                sa_flags: 0,
                 sa_restorer: None, // set by platform if applicable
                 sa_mask: sigset_t::default(),
             };

src/platform/redox/signal.rs

@@ -127,7 +127,7 @@ impl PalSignal for Sys {
                 SigactionKind::Ignore
             } else {
                 SigactionKind::Handled {
-                    handler: if c_act.sa_flags & crate::header::signal::SA_SIGINFO as c_int != 0 {
+                    handler: if c_act.sa_flags & crate::header::signal::SA_SIGINFO as c_ulong != 0 {
                         SignalHandler {
                             sigaction: unsafe { core::mem::transmute(c_act.sa_handler) },
                         }
@@ -170,7 +170,7 @@ impl PalSignal for Sys {
                         unsafe { handler.handler }
                     },
                     sa_restorer: None,
-                    sa_flags: old_action.flags.bits() as c_int,
+                    sa_flags: old_action.flags.bits() as c_ulong,
                     sa_mask: old_action.mask,
                 },
             };