use the calling user UID:GID as portage inside the container

The docker container creates the distfiles as "portage" user (UID 250)
in the host. This produces an error if then a container is launched as
podman. With this ugly hack we can get docker to fetch distfiles as the
calling user which avoids an error if then podman is used.

Author: stkw0

ebuildtester/docker.py

@@ -261,6 +261,7 @@ def _tweak_settings(self):
 
         # Avoid wasting time generating the whole set
         self.execute('echo "C.UTF-8 UTF-8" > /etc/locale.gen')
+        self.execute(f'sed -i "s/250/{os.getuid()}/g" /etc/passwd')
 
     def _get_repo_names(self, overlay_dirs):
         """Get repo names from local overlay settings."""