<pty.h>: linux only

not only Apple but also other OSes except Linux uses <util.h>.
for details, see
https://www.gnu.org/software/gnulib/manual/html_node/pty_002eh.html

PseudoTTYController.cpp

@@ -32,10 +32,10 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <termios.h>
-#if defined(__APPLE__)
+#if defined(__linux__)
-	#include <util.h>
-#else
 	#include <pty.h>
+#else
+	#include <util.h>
 #endif