standardize on amd64 artifact suffix

Author: lihaoyi

dist/package.mill

@@ -346,7 +346,13 @@ object `package` extends RootModule with InstallModule {
       else "linux"
     }
 
-    def artifactCpuSuffix = T { System.getProperty("os.arch") }
+    def artifactCpuSuffix = T {
+      System.getProperty("os.arch") match{
+        case "x64" => "amd64"
+        case s => s
+      }
+    }
+
     def artifactName = s"${super.artifactName()}-${artifactOsSuffix()}-${artifactCpuSuffix()}"
 
     def mainClass = Some("mill.runner.client.MillClientMain")