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/distcheck.yml

@@ -288,7 +288,8 @@ jobs:
             sha256sum pkg.bin && sha256sum pkg.bin | grep -qwF -- "${OLD_CMAKE_SHA256_WIN_INTEL}" && unzip -q pkg.bin && rm -f pkg.bin
             printf '%s' ~/cmake-"${OLD_CMAKE_VERSION}"-win64-x64/bin/cmake.exe > ~/old-cmake-path.txt
           elif [[ "${MATRIX_IMAGE}" = *'ubuntu'* ]]; then
-            sudo apt-get -o Dpkg::Use-Pty=0 install libpsl-dev libssl-dev
+            printf '#!/bin/sh\nfor i in 1 2 3; do timeout 30 "$@" && break; echo "Error: slow server, retry"; sleep 1; done' > "$HOME"/my-apt; chmod +x "$HOME"/my-apt
+            sudo "$HOME"/my-apt apt-get -o Dpkg::Use-Pty=0 install libpsl-dev libssl-dev
             cd ~
             curl --disable --fail --silent --show-error --connect-timeout 15 --max-time 60 --retry 3 --retry-connrefused \
               --location "https://github.com/Kitware/CMake/releases/download/v${OLD_CMAKE_VERSION}/cmake-${OLD_CMAKE_VERSION}-Linux-aarch64.tar.gz" --output pkg.bin