Closes #46365

The behavior I'm trying to handle here is documented in
https://man7.org/linux/man-pages/man5/proc_pid_exe.5.html.

[@merlinz01

](https://github.com/zed-industries/zed/issues/46365#issuecomment-3723996684)
points to some other alternatives but they don't seem necessary or
justified here.

# Testing

I've manually replaced the binary of a process running this build, to
simulate an update, and then opened a new tree and I don't see the error
message.

I don't know if there's a reasonable way to unit-test this? Let me know.
It seems like it would require using something like rusty-fork to spawn
a specific binary for the test, which I don't think I see already in the
Zed tree and perhaps it would be overkill to add just for this?


Release Notes:

- Fixed "Failed to load environment variables" after applying an update