Add a get_random_bytes() syscall to replace the SRPC-based implementation

src/trusted/service_runtime/BUILD.gn

 # Copyright (c) 2014 The Native ClientAuthors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 #  Generated from GYP
 
 if (is_posix) {
   syscall_handler_in = "posix/nacl_syscall_impl.c"
 } else {
   syscall_handler_in = "win/nacl_syscall_impl.c"
@@ skipping 72 matching lines @@
     "sel_qualify.c",
     "sel_validate_image.c",
     "sys_exception.c",
     "sys_fdio.c",
     "sys_filename.c",
     "sys_futex.c",
     "sys_imc.c",
     "sys_list_mappings.c",
     "sys_memory.c",
     "sys_parallel_io.c",
+    "sys_random.c",
     "thread_suspension_common.c",
     "thread_suspension_unwind.c",
   ]
 
   if (os == "linux") {
     sources += [
       "linux/nacl_signal.c",
     ]
     if (cpu_arch == "x86") {
       sources += ["linux/nacl_signal_32.c"]
@@ skipping 163 matching lines @@
     libs = ["rt"]
     ldflags = ["-pie"]
   }
   if (is_linux) {
     datadeps = [
       "//native_client/src/trusted/service_runtime/linux:nacl_helper_bootstrap"
     ]
   }
 }