[Feature] facilitate autogen.bat

[reg31]

Hi,

As a nice-to-have, you could add cd %~dp0 to autogen.bat so this will garantee that the script runs in current folder, such as:

@echo off
cd %~dp0
REM Run this to set up the build system: configure, makefiles, etc.

https://github.com/xiph/opus/blob/main/autogen.bat

This will allow to run the script simply by double click on Windows, instead of having to fire the terminal, navigate to the folder and run the script from here.