try to find patch.exe in git default installation folder (microsoft#17106)

### Description
updates the build.bat file in root folder to try best efforts to locate
patch.exe.

patch.exe is needed to apply patches to some of the dependencies. for
example, microsoft#17104. However, patch.exe is not available on every windows
developer's search path, and if cannot find patch.exe, the build will
continue silently. ( as a result, patch is not applied and for patches
like microsoft#17104, this will cause a build break )

This change adds folder `C:\Program Files\Git\usr\bin` to the PATH,
which is the default git installation directory. This may resolve the
patch not found issue for most (hopefully) users.

Author: fs-eire

build.bat

@@ -2,5 +2,9 @@
 :: Licensed under the MIT License.
 
 @echo off
+
+setlocal
+set PATH=C:\Program Files\Git\usr\bin;%PATH%
+
 rem Requires a Python install to be available in your PATH
 python "%~dp0\tools\ci_build\build.py" --build_dir "%~dp0\build\Windows" %*