feat: use known good axoupdater version

Instead of always fetching the latest axoupdater, fetch the version that this
version of dist itself uses as a library. That way, we're always fetching
something predictable.

cargo-dist/src/lib.rs

@@ -251,10 +251,13 @@ fn run_build_step(
     Ok(())
 }
 
-const AXOUPDATER_ASSET_ROOT: &str =
-    "https://github.com/axodotdev/axoupdater/releases/latest/download";
+const AXOUPDATER_ASSET_ROOT: &str = "https://github.com/axodotdev/axoupdater/releases";
 const AXOUPDATER_MINIMUM_VERSION: &str = "0.7.0";
 
+fn axoupdater_asset_root() -> String {
+    format!("{AXOUPDATER_ASSET_ROOT}/download/v{}", axoupdater::VERSION)
+}
+
 /// Fetches an installer executable and installs it in the expected target path.
 pub fn fetch_updater(dist_graph: &DistGraph, updater: &UpdaterStep) -> DistResult<()> {
     let ext = if updater.target_triple.is_windows() {
@@ -263,7 +266,8 @@ pub fn fetch_updater(dist_graph: &DistGraph, updater: &UpdaterStep) -> DistResul
         ".tar.xz"
     };
     let expected_url = format!(
-        "{AXOUPDATER_ASSET_ROOT}/axoupdater-cli-{}{ext}",
+        "{}/axoupdater-cli-{}{ext}",
+        axoupdater_asset_root(),
         updater.target_triple
     );