deb: fix concurrent testing (by making them serial)

Co-authored-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>
Co-committed-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>

src/context/unshare.rs

@@ -112,27 +112,41 @@ impl ContextDriver for UnshareDriver {
     }
 
     fn create_temp_dir(&self) -> io::Result<String> {
-        // Create a temporary directory inside the chroot
-        let timestamp = std::time::SystemTime::now()
+        // Create a temporary directory inside the chroot with unique naming
+        let base_timestamp = std::time::SystemTime::now()
             .duration_since(std::time::UNIX_EPOCH)
             .unwrap()
             .as_secs();
 
-        let work_dir_name = format!("pkh-build-{}", timestamp);
-        let work_dir_inside_chroot = format!("/tmp/{}", work_dir_name);
+        let mut attempt = 0;
+        loop {
+            let work_dir_name = if attempt == 0 {
+                format!("pkh-build-{}", base_timestamp)
+            } else {
+                format!("pkh-build-{}-{}", base_timestamp, attempt)
+            };
 
-        // Create the directory on the host filesystem
-        let host_path = Path::new(&self.path).join("tmp").join(&work_dir_name);
-        std::fs::create_dir_all(&host_path)?;
+            let work_dir_inside_chroot = format!("/tmp/{}", work_dir_name);
+            let host_path = Path::new(&self.path).join("tmp").join(&work_dir_name);
 
-        debug!(
-            "Created work directory: {} (host: {})",
-            work_dir_inside_chroot,
-            host_path.display()
-        );
+            // Check if directory already exists
+            if host_path.exists() {
+                attempt += 1;
+                continue;
+            }
 
-        // Return the path as it appears inside the chroot
-        Ok(work_dir_inside_chroot)
+            // Create the directory on the host filesystem
+            std::fs::create_dir_all(&host_path)?;
+
+            debug!(
+                "Created work directory: {} (host: {})",
+                work_dir_inside_chroot,
+                host_path.display()
+            );
+
+            // Return the path as it appears inside the chroot
+            return Ok(work_dir_inside_chroot);
+        }
     }
 
     fn copy_path(&self, src: &Path, dest: &Path) -> io::Result<()> {