Fix unittests.

Author: Alexhuszagh

xtask/src/util.rs

@@ -343,7 +343,7 @@ mod tests {
 
         let root = project_dir(&mut msg_info)?;
         let docker = root.join("docker");
-        let path = docker.join("Dockerfile.ubuntu");
+        let path = docker.join("Dockerfile.base.ubuntu");
 
         let dockerfile = fs::read_to_string(&path)?;
         let lines: Vec<&str> = dockerfile.lines().collect();