libvpx: use bsd-compatible sed expressions

third_party/libvpx/generate_gni.sh

 #!/bin/bash -e
 #
 # Copyright (c) 2012 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.
 
 # This script is used to generate .gni files and files in the
 # config/platform directories needed to build libvpx.
 # Every time libvpx source code is updated just run this script.
 #
@@ skipping 253 matching lines @@
 
 # Generate Config files. "--enable-external-build" must be set to skip
 # detection of capabilities on specific targets.
 # $1 - Header file directory.
 # $2 - Config command line.
 function gen_config_files {
   ./configure $2 > /dev/null
 
   # Disable HAVE_UNISTD_H as it causes vp8 to try to detect how many cpus
   # available, which doesn't work from inside a sandbox on linux.
-  sed -i.bak -e 's/\(HAVE_UNISTD_H\s\+\)1/\10/' vpx_config.h
+  sed -i.bak -e 's/\(HAVE_UNISTD_H[[:space:]]*\)1/\10/' vpx_config.h
   rm vpx_config.h.bak
 
   # Use the correct ads2gas script.
   if [[ "$1" == linux* ]]; then
     local ASM_CONV=ads2gas.pl
   else
     local ASM_CONV=ads2gas_apple.pl
   fi
 
   # Generate vpx_config.asm. Do not create one for mips or native client.
@@ skipping 177 matching lines @@
 cd $BASE_DIR
 rm -rf $TEMP_DIR
 
 gn format --in-place $BASE_DIR/BUILD.gn
 gn format --in-place $BASE_DIR/libvpx_srcs.gni
 
 cd $BASE_DIR/$LIBVPX_SRC_DIR
 update_readme
 
 cd $BASE_DIR