Set working directory on Windows to avoid UNC path warning

[nagayasu-shinya]

When running autoadb from a UNC path (e.g. WSL's \\wsl.localhost\...), cmd.exe prints a warning:

  '\\wsl.localhost\Ubuntu-24.04\home\nagayasu\work\autoadb'
  CMD.EXE was started with the above path as the current directory.
  UNC paths are not supported. Defaulting to Windows directory.

This sets the working directory to C:\ on Windows before spawning the child process, suppressing the warning.

Tested on

• WSL2 (Ubuntu 24.04) running autoadb.exe cross-compiled with x86_64-pc-windows-gnu

Before

$ target/x86_64-pc-windows-gnu/release/autoadb.exe cmd.exe /C echo {}
Detected device 5e524998
'\wsl.localhost\Ubuntu-24.04\home\nagayasu\work\autoadb'
  CMD.EXE was started with the above path as the current directory.
  UNC paths are not supported. Defaulting to Windows directory.
5e524998

after

$ target/x86_64-pc-windows-gnu/release/autoadb.exe cmd.exe /C echo {}
Detected device 5e524998
5e524998