Ensure selfupdate is enabled for SDKMAN! (#954)

* Ensure `selfupdate` is enabled for SDKMAN!

This subcommand is unavailable when the `sdkman_selfupdate_feature`
option is disabled, as is the case when SDKMAN! is installed via
Homebrew.

https://github.com/sdkman/sdkman-cli/pull/1042

* Fix macOS build; simplify

Co-authored-by: Roey Darwish Dror <roey.ghost@gmail.com>

Cargo.toml

@@ -41,6 +41,7 @@ notify-rust = "4.5.0"
 
 [target.'cfg(unix)'.dependencies]
 nix = "0.24.1"
+rust-ini = "0.18.0"
 self_update_crate = { version = "0.30.0", default-features = false, optional = true, package = "self_update", features = ["archive-tar", "compression-flate2", "rustls"] }
 
 [target.'cfg(windows)'.dependencies]
@@ -48,9 +49,6 @@ self_update_crate = { version = "0.30.0", default-features = false, optional = t
 winapi = "0.3.9"
 parselnk = "0.1.0"
 
-[target.'cfg(target_os = "linux")'.dependencies]
-rust-ini = "0.18.0"
-
 [profile.release]
 lto = true