Rollup merge of #52846 - kennytm:bootstrap-curl-timeout, r=Mark-Simulacrum

Add timeout to use of `curl` in bootstrap.py.

Recently we've seen a lot of "30 minutes no output" spurious errors while downloading the bootstrap compiler. This added several timeout options so if the "30 minutes no output" errors were caused by connection or transfer issue, we could fail quicker for curl to retry.

src/bootstrap/bootstrap.py

@@ -88,7 +88,10 @@ def _download(path, url, probably_big, verbose, exception):
             option = "-#"
         else:
             option = "-s"
-        run(["curl", option, "--retry", "3", "-Sf", "-o", path, url],
+        run(["curl", option,
+             "-y", "30", "-Y", "10",    # timeout if speed is < 10 bytes/sec for > 30 seconds
+             "--connect-timeout", "30", # timeout if cannot connect within 30 seconds
+             "--retry", "3", "-Sf", "-o", path, url],
             verbose=verbose,
             exception=exception)