This is a breaking change for cases where the environment is
accessed in a Command::pre_exec closure. Except for
single-threaded programs these uses were not correct
anyway since they aren't async-signal safe.
The test command-setgroups.rs is adjusted to skip on musl, where
`sysconf(_SC_NGROUPS_MAX)` always returns a dummy value of 32,
even though the actual value is 65536. I'm not sure why this becomes
relevant only now though, as this was apparently the case since
kernel 2.6.4.
This stabilizes process_set_argv0 targeting 1.45.0. It has been
useful in practice and seems useful as-is.
The equivalent feature could be implemented for Windows, but as far as I
know nobody has. That can be done separately.
Tracking issue: #66510
