将unistd.c不再放在common中，分散到各个库中

components/libc/compilers/armlibc/unistd.c

@@ -11,6 +11,8 @@
 #include <termios.h>
 #include <unistd.h>
 
+#ifdef RT_USING_POSIX
+
 #ifdef RT_USING_POSIX_TERMIOS
 int isatty(int fd)
 {
@@ -23,3 +25,5 @@ char *ttyname(int fd)
 {
     return "/dev/tty0"; /*TODO: need to add more specific*/
 }
+
+#endif

components/libc/compilers/dlib/unistd.c

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2006-2018, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2020-09-01     Meco Man     First Version
+ */
+
+#include <termios.h>
+#include <unistd.h>
+
+#ifdef RT_USING_POSIX
+
+#ifdef RT_USING_POSIX_TERMIOS
+int isatty(int fd)
+{
+    struct termios ts;
+    return(tcgetattr(fd,&ts) != -1);/*true if no error (is a tty)*/
+}
+#endif
+
+char *ttyname(int fd)
+{
+    return "/dev/tty0"; /*TODO: need to add more specific*/
+}
+
+#endif

components/libc/compilers/newlib/unistd.c

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2006-2018, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2020-09-01     Meco Man     First Version
+ */
+
+#include <termios.h>
+#include <unistd.h>
+
+#ifdef RT_USING_POSIX
+
+#ifdef RT_USING_POSIX_TERMIOS
+int isatty(int fd)
+{
+    struct termios ts;
+    return(tcgetattr(fd,&ts) != -1);/*true if no error (is a tty)*/
+}
+#endif
+
+char *ttyname(int fd)
+{
+    return "/dev/tty0"; /*TODO: need to add more specific*/
+}
+
+#endif