update(install): retry a busy disk-image attach for about a minute

crates/update/src/install.rs

@@ -1307,8 +1307,9 @@ pub mod macos {
                     Duration::from_secs(300),
                 )
             };
+            // diskimages-helper can stay busy for a while on a shared runner; a minute of retries is still quick.
             let mut attached = attach();
-            for wait in [1, 2, 4, 8] {
+            for wait in [1, 2, 4, 8, 16, 32] {
                 if attached.is_ok() {
                     break;
                 }