Update ninja version in shell script too.

ninja

 #!/usr/bin/env bash
 
 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 OS="$(uname -s)"
 THIS_DIR="$(dirname "${0}")"
 
 function print_help() {
 cat <<-EOF
 No prebuilt ninja binary was found for this system.
 Try building your own binary by doing:
   cd ~
-  git clone https://github.com/martine/ninja.git -b v1.6.0
+  git clone https://github.com/martine/ninja.git -b v1.7.1
   cd ninja && ./configure.py --bootstrap
 Then add ~/ninja/ to your PATH.
 EOF
 }
 
 case "$OS" in
   Linux)
     MACHINE=$(uname -m)
     case "$MACHINE" in
       i?86|x86_64)
         LONG_BIT=$(getconf LONG_BIT)
         # We know we are on x86 but we need to use getconf to determine
         # bittage of the userspace install (e.g. when runing 32-bit userspace
         # on x86_64 kernel)
         exec "${THIS_DIR}/ninja-linux${LONG_BIT}" "$@";;
       *)
         echo Unknown architecture \($MACHINE\) -- unable to run ninja.
         print_help
         exit 1;;
     esac
     ;;
   Darwin)    exec "${THIS_DIR}/ninja-mac" "$@";;
   CYGWIN*)   exec cmd.exe /c $(cygpath -t windows $0).exe "$@";;
   MINGW*)    cmd.exe //c $0.exe "$@";;
   *)         echo "Unsupported OS ${OS}"
              print_help
              exit 1;;
 esac