main: do not exit in case stdin is a closed stream

Weston should not exit if stdin is a closed stream. This allows
to launch with a closed stdin:

  # weston <&-

This fixes screen sharing using weston: Weston closes the stdin
before forking itself to execute the screen sharing instance of
weston. Before this patch screen sharing failed with:
  Screen share failed: No wl_shm found
  unknown child process exited

Fixes: f0d39b2243 ("weston: Set CLOEXEC on stdin")
Signed-off-by: Stefan Agner <stefan@agner.ch>

compositor/main.c

@@ -2548,10 +2548,7 @@ int main(int argc, char *argv[])
 
 	wl_list_init(&wet.layoutput_list);
 
-	if (os_fd_set_cloexec(fileno(stdin))) {
-		printf("Unable to set stdin as close on exec().\n");
-		return EXIT_FAILURE;
-	}
+	os_fd_set_cloexec(fileno(stdin));
 
 	cmdline = copy_command_line(argc, argv);
 	parse_options(core_options, ARRAY_LENGTH(core_options), &argc, argv);