deb: fix bugs on injecting packages/ppa

- ppa was not the right target_arch if binfmt was used
- apt-get would not downgrade for injected packages, but we want to

src/deb/local.rs

@@ -70,7 +70,7 @@ pub async fn build(
             if !sources.iter().any(|s| s.uri.contains(&base_url)) {
                 // Get host and target architectures
                 let host_arch = crate::get_current_arch();
-                let target_arch = if cross { arch } else { &host_arch };
+                let target_arch = arch;
 
                 // Create architectures list with both host and target if different
                 let mut architectures = vec![host_arch.clone()];
@@ -174,6 +174,7 @@ pub async fn build(
         let mut cmd = ctx.command("apt-get");
         cmd.envs(env.clone())
             .arg("-y")
+            .arg("--allow-downgrades")
             .arg("install")
             .args(packages);
         let status = cmd.status()?;