Stub out macos setup

Just enough to get it compiling on CI

src/setup.rs

@@ -12,6 +12,11 @@ mod linux;
 #[cfg(target_os = "linux")]
 use linux as imp;
 
+#[cfg(target_os = "macos")]
+mod macos;
+#[cfg(target_os = "macos")]
+use macos as imp;
+
 pub fn setup() {
     println!("Welcome to Oxidux!");
     if let Err(e) = try_setup() {

src/setup/linux.rs

@@ -6,8 +6,7 @@ use std::process::Command;
 
 use eyre::{bail, eyre, WrapErr};
 
-use super::SetupArgs;
-use super::SetupResult;
+use super::{SetupArgs, SetupResult};
 
 pub(super) fn setup(args: &SetupArgs) -> SetupResult {
     verify_tld_resolver(args)?;

src/setup/macos.rs

@@ -0,0 +1,5 @@
+use super::{SetupArgs, SetupResult};
+
+pub(super) fn setup(args: &SetupArgs) -> SetupResult {
+    todo!("MacOS setup not yet implemented");
+}