Add Python 3.8 to py based search in find_python.bat (GH-17188)

Author: segevfiner

PCbuild/find_python.bat

@@ -37,7 +37,7 @@
 @if NOT "%HOST_PYTHON%"=="" @%HOST_PYTHON% -Ec "import sys; assert sys.version_info[:2] >= (3, 6)" >nul 2>nul && (set PYTHON="%HOST_PYTHON%") && (set _Py_Python_Source=found as HOST_PYTHON) && goto :found
 
 @rem If py.exe finds a recent enough version, use that one
-@for %%p in (3.7 3.6) do @py -%%p -EV >nul 2>&1 && (set PYTHON=py -%%p) && (set _Py_Python_Source=found %%p with py.exe) && goto :found
+@for %%p in (3.8 3.7 3.6) do @py -%%p -EV >nul 2>&1 && (set PYTHON=py -%%p) && (set _Py_Python_Source=found %%p with py.exe) && goto :found
 
 @if NOT exist "%_Py_EXTERNALS_DIR%" mkdir "%_Py_EXTERNALS_DIR%"
 @set _Py_NUGET=%NUGET%