fix(py): set `cwd` when get commit sha in setup.py (#14299)
fix(py): set `cwd` when get commit sha in setup.py (#14299)

`cwd` was not set before when get commit SHA. The default `cwd` is the current build directory. However, the build directory might not be the subdirectory of source. The `git` command will fail when that happened.

test=develop
chengduoZH/Paddle,baidu/Paddle,tensor-tang/Paddle,tensor-tang/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,luotao1/Paddle,baidu/Paddle,chengduoZH/Paddle,tensor-tang/Paddle,baidu/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,luotao1/Paddle,baidu/Paddle,chengduoZH/Paddle,luotao1/Paddle,chengduoZH/Paddle,luotao1/Paddle,baidu/Paddle,luotao1/Paddle,chengduoZH/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,luotao1/Paddle