potential upcoming macOS breakage around launchctl setenv

[abathur]

Noticed a report of trouble percolating in CI that may start affecting this installer as well. My comment for context:

• fail to run on macos-latest cachix/install-nix-action#183 (comment)

Invocation here:

nix-installer/src/action/common/configure_init_service.rs

Lines 214 to 221 in 47f2630

	execute_command(
	Command::new("launchctl")
	.process_group(0)
	.arg("setenv")
	.arg("NIX_SSL_CERT_FILE")
	.arg(format!("{ssl_cert_file:?}"))
	.stdin(std::process::Stdio::null()),
	)

Nix 2.15+ happens to have a new config option that should skirt the need to use launchctl for this?

• Add a setting for configuring the SSL certificates file NixOS/nix#8062