Remove unused support for SysV shared memory

src/trusted/desc/BUILD.gn

 # Copyright 2014 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 group("all_desc") {
   deps = [
     ":desc_wrapper",
     ":nrd_xfer"
   ]
 }
@@ skipping 35 matching lines @@
     "nacl_desc_sync_socket.c",
     "nacl_desc_sync_socket.h",
     "nrd_all_modules.c",
     "nrd_all_modules.h",
     "nrd_xfer.c",
     "nrd_xfer.h",
     "nrd_xfer_intern.h",
   ]
 
   if (os == "linux") {
-    sources += [
-      "linux/nacl_desc_sysv_shm.c",
-      "linux/nacl_desc_sysv_shm.h",
-      "posix/nacl_desc.c",
-    ]
+    sources += ["posix/nacl_desc.c"]
   }
 
   if (os == "mac") {
     sources += ["posix/nacl_desc.c"]
   }
 
   if (os == "win") {
     sources += [
       "win/nacl_desc.c",
       "nacl_desc_conn_cap.c",
       "nacl_desc_imc_bound_desc.c",
       "nacl_makeboundsock.c",
     ]
   } else {
     sources += [
       "posix/nacl_desc_conn_cap.c",
       "posix/nacl_desc_imc_bound_desc.c",
       "posix/nacl_makeboundsock.c",
     ]
   }
 }
 
 static_library("desc_wrapper") {
   include_dirs = ["."]
   sources = [
     "nacl_desc_wrapper.cc"
   ]
 }