This provides a platform-independent way to configure the SSL
certificates file in the Nix daemon. Previously we provided
instructions for overriding the environment variable in launchd, but
that obviously doesn't work with systemd. Now we can just tell users
to add
ssl-cert-file = /etc/ssl/my-certificate-bundle.crt
to their nix.conf.
The default maxfiles on macOS 11 and macOS 12 is 256, which is too low
for nix to work:
```
$ launchctl limit maxfiles
maxfiles 256 unlimited
```
Set NumberOfFiles of nix-daemon to 4096 to avoid `Too many open files`
error.
Mac OS multi-user installations are currently broken because all requests
made by nix-daemon to the binary cache fail with:
```
unable to download ... Problem with the SSL CA cert (path? access rights?) (77).
```
This change ensures that the nix-daemon knows where to find the SSL CA cert file.
Fixes#2899 and #3261.
We're calling `wait4path` on the full, resolved `@bindir@/nix-daemon` path.
That means we're hardcoding something like:
/bin/wait4path /nix/store/zs9c5xhp3zv9p23qnjxp87nl5injsi1i-nix-2.3/bin/nix-daemon && /nix/var/nix/profiles/default/bin/nix-daemon
That seems unnecessarily fragile.
It might be better to wait4path on the path we intend to call.
On Catalina, the /nix filesystem might not be mounted at start time.
To avoid this service not starting, we need to keep the launch agent
outside of the Nix store. A wait4pid will hold for our /nix dir to be
mounted.
Fixes#3125.
When using a volume, the nix-daemon path may not exist. To avoid this
issue, we must use the wait4path tool. This should solve one of the
issues in multi-user on macOS Catalina.
Since macOS 10.14 this has become an error, causing problems if the
nix-daemon loads nix during substitution (this is a forked process).
Workaround for #2523.
