Permit downloads of any channel artifact

We recently landed beta artifacts on the master branch for some time which broke
perf, and this should avoid breaking perf if that happens in the future. In
theory it should also let us benchmark beta/stable PRs if that ever becomes
necessary without as much hassle.

Author: Mark-Simulacrum

collector/src/sysroot.rs

@@ -94,17 +94,18 @@ impl fmt::Display for ModuleVariant {
 }
 
 impl ModuleVariant {
-    fn url(&self, sysroot: &SysrootDownload, triple: &str) -> String {
+    fn url(&self, channel: &str, sysroot: &SysrootDownload, triple: &str) -> String {
         let suffix = if *self == ModuleVariant::RustSrc {
             String::new()
         } else {
             format!("-{}", triple)
         };
         format!(
-            "{base}/{sha}/{module}-nightly{suffix}.tar.xz",
+            "{base}/{sha}/{module}-{channel}{suffix}.tar.xz",
             base = BASE_URL,
             module = self,
             sha = sysroot.rust_sha,
+            channel = channel,
             suffix = suffix,
         )
     }
@@ -151,26 +152,34 @@ impl SysrootDownload {
             }
         }
 
-        let url = variant.url(self, &self.triple);
-        log::debug!("requesting: {}", url);
-        let resp = reqwest::blocking::get(&url)?;
-        log::debug!("{}", resp.status());
-        if resp.status().is_success() {
-            let reader = XzDecoder::new(BufReader::new(resp));
-            match self.extract(variant, reader) {
-                Ok(()) => return Ok(()),
-                Err(err) => {
-                    log::warn!("extracting {} failed: {:?}", url, err);
+        // We usually have nightlies but we want to avoid breaking down if we
+        // accidentally end up with a beta or stable commit.
+        let urls = [
+            variant.url("nightly", self, &self.triple),
+            variant.url("beta", self, &self.triple),
+            variant.url("stable", self, &self.triple),
+        ];
+        for url in &urls {
+            log::debug!("requesting: {}", url);
+            let resp = reqwest::blocking::get(url)?;
+            log::debug!("{}", resp.status());
+            if resp.status().is_success() {
+                let reader = XzDecoder::new(BufReader::new(resp));
+                match self.extract(variant, reader) {
+                    Ok(()) => return Ok(()),
+                    Err(err) => {
+                        log::warn!("extracting {} failed: {:?}", url, err);
+                    }
                 }
             }
         }
 
         return Err(anyhow!(
-            "unable to download sha {} triple {} module {} from {}",
+            "unable to download sha {} triple {} module {} from any of {:?}",
             self.rust_sha,
             self.triple,
             variant,
-            url
+            urls
         ));
     }