efi: to get esp part during installation, if failed via

`/dev/disk/by-partlabel`, change to `sfdisk`

During `bootc install to-disk`, the esp device is not mounted and
will call `get_esp_device()` to get esp device via
`/dev/disk/by-partlabel/`.
When running `cosa build`, the efi part is mounted and can not get
get esp device via `/dev/disk/by-partlabel`, with this patch,
change to `sfdik` to get esp part.

Author: HuijingHei

src/efi.rs

@@ -321,10 +321,16 @@ impl Component for Efi {
         log::debug!("Found metadata {}", meta.version);
         let srcdir_name = component_updatedirname(self);
         let ft = crate::filetree::FileTree::new_from_dir(&src_root.sub_dir(&srcdir_name)?)?;
-        // get esp device via /dev/disk/by-partlabel
-        let esp_device = self
-            .get_esp_device()
-            .ok_or_else(|| anyhow::anyhow!("Failed to find ESP device"))?;
+
+        // Get esp device via /dev/disk/by-partlabel
+        // If failed, change to sfdisk
+        let esp_device = if let Some(esp) = self.get_esp_device() {
+                esp
+            } else {
+                let esp = blockdev::get_esp_partition(device)?
+                    .ok_or_else(|| anyhow::anyhow!("Failed to find ESP device"))?;
+                PathBuf::from(esp)
+            };
         let destpath = &self.ensure_mounted_esp(Path::new(dest_root), &esp_device)?;
 
         let destd = &openat::Dir::open(destpath)