.out and .err files should be created in a temp dir

[rdicroce]

Currently, the .out and .err files are created in the working directory, or the workspace directory if the working directory is not set. This is a problem because it means the files are inside the Git repo. I have an automated release workflow that updates some files and commits them, and the .out and .err files got accidentally committed to the repo because of that.

So I suggest that the .out and .err files should be created in a temp directory outside the workspace instead. The RUNNER_TEMP environment variable provides a temp directory that you could use.