noux: add local nanosleep(2) and sleep(3)

Up to now Noux used the libc sleep functions, which actually is not
possible because the _nanosleep() function implemented by our libc
creates a new thread to handle the timeout. Noux childs may have
only one thread, e.g., the main thread, though. To fix this issue
sleeping is now handled directly by Noux. It is implemented by calling
select(2) with a timeout. This fix is needed for mutt(1), which calls
sleep when it prints a notification for the user.

Fixes #1374.

repos/ports/src/lib/libc_noux/plugin.cc

@@ -657,6 +657,50 @@ extern "C" int kill(int pid, int sig)
 }
 
 
+extern "C" int nanosleep(const struct timespec *timeout,
+                         struct timespec *remainder)
+{
+	Noux::Sysio::Select_fds &in_fds = sysio()->select_in.fds;
+
+	in_fds.num_rd = 0;
+	in_fds.num_wr = 0;
+	in_fds.num_ex = 0;
+
+	sysio()->select_in.timeout.sec  = timeout->tv_sec;
+	sysio()->select_in.timeout.usec = timeout->tv_nsec / 1000;
+
+	/*
+	 * Perform syscall
+	 */
+	if (!noux_syscall(Noux::Session::SYSCALL_SELECT)) {
+		switch (sysio()->error.select) {
+		case Noux::Sysio::SELECT_ERR_INTERRUPT: errno = EINTR; break;
+		}
+
+		return -1;
+	}
+
+	if (remainder) {
+		remainder->tv_sec  = 0;
+		remainder->tv_nsec = 0;
+	}
+
+	return 0;
+}
+
+
+extern "C" unsigned int sleep(unsigned int seconds)
+{
+	struct timespec dummy = { seconds, 0 };
+
+	/*
+	 * Always return 0 because our nanosleep() cannot not be interrupted.
+	 */
+	nanosleep(&dummy, 0);
+	return 0;
+}
+
+
 /********************
  ** Time functions **
  ********************/