Instruct build agent to clean the logs

If the build logs are left in the current directory, the backport/rebase
agent can decide to analyze them on its own, and that can have unwanted
effects. It should always use just the summary it was given by the build
agent.

Signed-off-by: Nikola Forró <[email protected]>

Author: nforro

agents/build_agent.py

@@ -34,7 +34,8 @@ def get_instructions() -> str:
       using the `download_artifacts` tool to the current directory. If there are no log files,
       just return the error message. Otherwise, start with `builder-live.log` and try to identify
       the build failure. If not found, try the same with `root.log`. Summarize the findings
-      and return them as `error`. If the build failed due to a build timeout, set `is_timeout` to `true` in your output.
+      and return them as `error`. If the build failed due to a build timeout, set `is_timeout` to `true`
+      in your output. Remove the downloaded *.log.gz files, if any.
 
       General instructions: