FS Locations can leak compiler information

We tell people to build by running cargo build generates a version of Arti. But doing so includes the absolute path of the user's cargo directory and of the current working directory in the generated binary. This can be personally identifying.

For more information see https://github.com/betrusted-io/xous-core/issues/57, and the issues that it links.

To see the extent of the issue, run:

cargo build -p arti --release
string target/release/arti | grep "$HOME"

Edited to add:

I have seen some logfile outputs where stack traces and locations and absolute paths contained user homedir locations, but I haven't been able to reproduce this myself.