Make git binary tools auto update on mingw

bootstrap/win/win_tools.bat

 @echo off
 :: 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 will try to find if svn and python are accessible and it not,
 :: it will try to download it and 'install' it in depot_tools.
 
 :: Sadly, we can't use SETLOCAL here otherwise it ERRORLEVEL is not correctly
 :: returned.
@@ skipping 46 matching lines @@
 goto :END
 
 :GIT_CHECK
 
 :: See if we're on XP
 for /f "tokens=2 delims=[]" %%i in ('ver') do set VERSTR=%%i
 for /f "tokens=2,3 delims=. " %%i in ("%VERSTR%") do (set VERMAJOR=%%i & set VERMINOR=%%j)
 if %VERMAJOR% lss 5 set GIT_VERSION=%GIT_VERSION%-xp
 if %VERMAJOR% equ 5 if %VERMINOR% lss 2 set XP_SUFFIX=-xp
 
+:: must explicitly use FIND_EXE to prevent this from grabbing e.g. gnuwin32 or
+:: msys versions.
+set FIND_EXE=%SYSTEMROOT%\System32\find.exe
+
 :: Check to see if we're on a 32 or 64 bit system
-reg Query "HKLM\Hardware\Description\System\CentralProcessor\0" | find /i "x86" > NUL && set OS_BITS=32 || set OS_BITS=64
+reg Query "HKLM\Hardware\Description\System\CentralProcessor\0" | %FIND_EXE% /i "x86" > NUL && set OS_BITS=32 || set OS_BITS=64
 
 if not exist "%WIN_TOOLS_ROOT_DIR%\.git_bleeding_edge" goto :GIT_OLD_FLOW
 set GIT_PORTABLE_FLOW=1
 set GIT_VERSION=2.7.4-%OS_BITS%
 set GIT_FETCH_URL=https://commondatastorage.googleapis.com/chrome-infra/PortableGit-%GIT_VERSION%-bit.7z.exe
 set GIT_DOWNLOAD_PATH=%ZIP_DIR%\git.7z.exe
 set GIT_BIN_DIR=git-%GIT_VERSION%_bin
 set GIT_INST_DIR=%WIN_TOOLS_ROOT_DIR%\%GIT_BIN_DIR%
 set GIT_EXE_PATH=%GIT_INST_DIR%\bin\git.exe
 goto :GIT_CLEANUP
@@ skipping 127 matching lines @@
 goto :END
 
 
 :returncode
 set WIN_TOOLS_ROOT_URL=
 set WIN_TOOLS_ROOT_DIR=
 exit /b %ERRORLEVEL%
 
 :END
 call :returncode %ERRORLEVEL%