[fusl] Don't syscall(SYS_ioctl, ...) in stdio

fusl/src/stdio/__fdopen.c

Index: fusl/src/stdio/__fdopen.c
diff --git a/fusl/src/stdio/__fdopen.c b/fusl/src/stdio/__fdopen.c
index 3a62f30bbf237879d50c51b14942ed47c516c7f1..eb72928708db8db730b016db89f88ffa8855fbd7 100644
--- a/fusl/src/stdio/__fdopen.c
+++ b/fusl/src/stdio/__fdopen.c
@@ -1,13 +1,12 @@
 #include "stdio_impl.h"
 #include <stdlib.h>
-#include <sys/ioctl.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <string.h>
+#include <unistd.h>
 
 FILE* __fdopen(int fd, const char* mode) {
   FILE* f;
-  struct winsize wsz;
 
   /* Check for valid initial mode character */
   if (!strchr("rwa", *mode)) {
@@ -44,7 +43,7 @@ FILE* __fdopen(int fd, const char* mode) {
 
   /* Activate line buffered mode for terminals */
   f->lbf = EOF;
-  if (!(f->flags & F_NOWR) && !__syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz))
+  if (!(f->flags & F_NOWR) && isatty(fd))
     f->lbf = '\n';
 
   /* Initialize op ptrs. No problem if some are unneeded. */