[newlib-cygwin] Cygwin: signal.cc: Include <unistd.h>

[Sebastian Huber]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6238b1877d3c83b8b9ed589494d0705386b7f4f7

commit 6238b1877d3c83b8b9ed589494d0705386b7f4f7
Author: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date:   Thu May 12 11:21:08 2022 +0200

    Cygwin: signal.cc: Include <unistd.h>
    
    Include <unistd.h> for sleep() and usleep() declarations.  Fix return type of
    usleep().

Diff:
---
 winsup/cygwin/signal.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/signal.cc b/winsup/cygwin/signal.cc
index 9b6c2509d..8175de07b 100644
--- a/winsup/cygwin/signal.cc
+++ b/winsup/cygwin/signal.cc
@@ -11,6 +11,7 @@ details. */
 
 #include "winsup.h"
 #include <stdlib.h>
+#include <unistd.h>
 #include <sys/cygwin.h>
 #include <sys/signalfd.h>
 #include "pinfo.h"
@@ -174,7 +175,7 @@ sleep (unsigned int seconds)
   return 0;
 }
 
-extern "C" unsigned int
+extern "C" int
 usleep (useconds_t useconds)
 {
   struct timespec req;