Add build target for nacl_io from the NaCl SDK.

native_client_sdk/src/libraries/nacl_io/library.dsc

 {
   'TOOLS': ['newlib', 'glibc', 'pnacl'],
   'SEARCH': [
     '.',
     'pepper',
     '../third_party/newlib-extras',
     'include',
   ],
   'TARGETS': [
     {
@@ skipping 77 matching lines @@
         "syscalls/inet_ntop.cc",
         "syscalls/ioctl.c",
         "syscalls/isatty.c",
         "syscalls/kill.c",
         "syscalls/killpg.c",
         "syscalls/lchown.c",
         "syscalls/link.c",
         "syscalls/listen.c",
         "syscalls/lstat.c",
         "syscalls/mkdir.c",
-        "syscalls/mount.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/recv.c",
         "syscalls/recvfrom.c",
         "syscalls/recvmsg.c",
         "syscalls/remove.c",
@@ skipping 150 matching lines @@
         "all_interfaces.h",
         "define_empty_macros.h",
         "undef_macros.h",
       ],
       'DEST': 'include/nacl_io/pepper',
     }
   ],
   'DEST': 'src',
   'NAME': 'nacl_io',
 }