GHA: try workaround for slow Azure Ubuntu distro server

It's been going on for almost a year, chances seem slim to have this
fixed upstream.

The observed issue is that on GitHub-supplied CI runner images,
sometimes, `apt-get install` using the stock distro server
`http://azure.archive.ubuntu.com/ubuntu` sees extreme slowness while
downloading data, then reaching the job timeout and aborting, making CI
red and necessitating a manual restart of the failed job(s).

In majority of cases the install step takes no longer than 8-40 seconds
(download + install), while in the failing case it takes 10-20+ minutes
just to download.

Earlier I slimmed down installs to avoid unnecessary packages, which
mitigated, but did not completely fix the issue.

Example:
https://github.com/curl/curl/actions/runs/23599596928/job/68725576899?pr=21105

Follow-up to 0455d8772a #18509

Closes #21107

.github/workflows/non-native.yml

@@ -348,7 +348,9 @@ jobs:
       fail-fast: false
     steps:
       - name: 'install packages'
-        run: sudo apt-get -o Dpkg::Use-Pty=0 install libfl2
+        run: |
+          printf '#!/bin/sh\nfor i in 1 2 3; do timeout 30 "$@" && break; echo "Error: slow server, retry"; sleep 1; done' > "$HOME"/my-apt; chmod +x "$HOME"/my-apt
+          sudo "$HOME"/my-apt apt-get -o Dpkg::Use-Pty=0 install libfl2
 
       - name: 'cache compiler (djgpp)'
         uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3