Move use_brlapi build flag to chrome.

build/linux/libbrlapi/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//tools/generate_library_loader/generate_library_loader.gni")
 
-config("brlapi_config") {
-  defines = [ "USE_BRLAPI" ]
-}
-
-# TODO(GYP) linux_link_brlapi support. Is this needed?
 generate_library_loader("libbrlapi") {
   name = "LibBrlapiLoader"
   output_h = "libbrlapi.h"
   output_cc = "libbrlapi_loader.cc"
   header = "<brlapi.h>"
-  config = ":brlapi_config"
 
   functions = [
     "brlapi_getHandleSize",
     "brlapi_error_location",
     "brlapi_strerror",
     "brlapi__acceptKeys",
     "brlapi__openConnection",
     "brlapi__closeConnection",
     "brlapi__getDisplaySize",
     "brlapi__enterTtyModeWithPath",
     "brlapi__leaveTtyMode",
     "brlapi__writeDots",
     "brlapi__readKey",
   ]
 }