[NaCl SDK] Add realpath(3) implementation.

native_client_sdk/src/libraries/nacl_io/library.dsc

 {
   'TOOLS': ['bionic', 'newlib', 'glibc', 'pnacl', 'linux'],
   'SEARCH': [
     '.',
     'pepper',
     '../third_party/newlib-extras',
     'include',
   ],
   'TARGETS': [
     {
@@ skipping 50 matching lines @@
         "socket/udp_event_emitter.cc",
         "socket/udp_node.cc",
         "stream/stream_event_emitter.cc",
         "stream/stream_fs.cc",
         "stream/stream_node.cc",
         "syscalls/accept.c",
         "syscalls/access.c",
         "syscalls/bind.c",
         "syscalls/cfgetispeed.c",
         "syscalls/cfgetospeed.c",
-        "syscalls/cfsetspeed.c",
         "syscalls/cfsetispeed.c",
         "syscalls/cfsetospeed.c",
+        "syscalls/cfsetspeed.c",
         "syscalls/chdir.c",
         "syscalls/chmod.c",
         "syscalls/chown.c",
         "syscalls/connect.c",
         "syscalls/fchdir.c",
         "syscalls/fchmod.c",
         "syscalls/fchown.c",
         "syscalls/fcntl.c",
         "syscalls/fdatasync.c",
         "syscalls/fdopen.c",
@@ skipping 27 matching lines @@
         "syscalls/lstat.c",
         "syscalls/mkdir.c",
         # Not called mount.c to avoid object file naming conflict with
         # mount.cc.
         "syscalls/syscall_mount.c",
         "syscalls/ntohl.c",
         "syscalls/ntohs.c",
         "syscalls/pipe.c",
         "syscalls/poll.c",
         "syscalls/readlink.c",
-        "syscalls/rmdir.c",
+        "syscalls/realpath.c",
         "syscalls/recv.c",
         "syscalls/recvfrom.c",
         "syscalls/recvmsg.c",
         "syscalls/remove.c",
         "syscalls/rename.c",
-        "syscalls/tcdrain.c",
-        "syscalls/tcflow.c",
-        "syscalls/tcflush.c",
-        "syscalls/tcgetattr.c",
-        "syscalls/tcsendbreak.c",
-        "syscalls/tcsetattr.c",
-        "syscalls/truncate.c",
+        "syscalls/rmdir.c",
         "syscalls/select.c",
         "syscalls/send.c",
         "syscalls/sendmsg.c",
         "syscalls/sendto.c",
         "syscalls/setsockopt.c",
         "syscalls/shutdown.c",
         "syscalls/sigaction.c",
         "syscalls/sigaddset.c",
         "syscalls/sigdelset.c",
         "syscalls/sigemptyset.c",
         "syscalls/sigfillset.c",
         "syscalls/sigismember.c",
         "syscalls/signal.c",
         "syscalls/sigpause.c",
         "syscalls/sigpending.c",
         "syscalls/sigset.c",
         "syscalls/sigsuspend.c",
         "syscalls/socket.c",
         "syscalls/socketpair.c",
         "syscalls/symlink.c",
-        "syscalls/unlink.c",
+        "syscalls/tcdrain.c",
+        "syscalls/tcflow.c",
+        "syscalls/tcflush.c",
+        "syscalls/tcgetattr.c",
+        "syscalls/tcsendbreak.c",
+        "syscalls/tcsetattr.c",
+        "syscalls/truncate.c",
         "syscalls/umount.c",
         "syscalls/uname.c",
+        "syscalls/unlink.c",
         "syscalls/utime.c",
         "syscalls/utimes.c",
       ],
     }
   ],
   'HEADERS': [
     {
       'FILES': [
         "char_node.h",
         "devfs/dev_fs.h",
@@ skipping 67 matching lines @@
     },
     {
       'FILES': [
         "arpa/inet.h",
         "memory.h",
         "netdb.h",
         "netinet/in.h",
         "netinet/tcp.h",
         "netinet6/in6.h",
         "poll.h",
+        "stdlib.h",
         "sys/ioctl.h",
         "sys/mount.h",
         "sys/poll.h",
         "sys/select.h",
         "sys/signal.h",
         "sys/socket.h",
         "sys/termios.h",
         "sys/utsname.h",
       ],
       'DEST': 'include/newlib',
     },
     {
       'FILES': [
         "arpa/inet.h",
         "memory.h",
         "netdb.h",
         "netinet/in.h",
         "netinet/tcp.h",
         "netinet6/in6.h",
         "poll.h",
+        "stdlib.h",
         "sys/ioctl.h",
         "sys/mount.h",
         "sys/poll.h",
         "sys/select.h",
         "sys/socket.h",
         "sys/termios.h",
         "sys/utsname.h",
       ],
       'DEST': 'include/pnacl',
     },
     {
       'FILES': [
         "poll.h",
         "sys/poll.h",
       ],
       'DEST': 'include/win',
     },
     {
       'FILES': [
         "all_interfaces.h",
         "define_empty_macros.h",
         "undef_macros.h",
       ],
       'DEST': 'include/nacl_io/pepper',
     }
   ],
   'DEST': 'src',
   'NAME': 'nacl_io',
 }