deb: use qemu_binfmt on ephemeral/local builds of different arch

src/deb/mod.rs

@@ -49,8 +49,15 @@ pub async fn build_binary_package(
     };
 
     // Create an ephemeral unshare context for all Local builds
+    // Use qemu_binfmt when target architecture differs from host and cross is not requested
+    let chroot_arch = if mode == BuildMode::Local && arch != current_arch && !cross {
+        Some(arch)
+    } else {
+        None
+    };
+
     let mut guard = if mode == BuildMode::Local {
-        Some(ephemeral::EphemeralContextGuard::new(series).await?)
+        Some(ephemeral::EphemeralContextGuard::new(series, chroot_arch).await?)
     } else {
         None
     };