Previously this code would run the changed commend, take its output,
remove the `marker` from the front and then split on `0` byte.
Problem was that `echo` adds a newline, which we did *NOT* skip. So
whatever `env` printed as the first environment variable would have a
`\n` in front of it.
Instead of setting, say, `HOME`, Zed would set `\nHOME`.
This change fixes the issue by switching to `printf '%s' marker`, which
is more portable than using `echo -n`.
This is related to https://github.com/zed-industries/zed/issues/9786 but
I'm not sure yet whether that fixes it.
Release Notes:
- Fixed Zed sometimes missing environment variables from shell in case
they were the first environment variable listed by `/usr/bin/env`.
7dbcace839