GHA: try workaround for slow Azure Ubuntu distro server (cont.)

- fail if all retries failed.
- run `dpkg --configure -a` after an aborted slow attempt.

```
Selecting previously unselected package libsys-hostname-long-perl.
Error: slow server, retry
E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.
[...]
```

Bug: https://github.com/curl/curl/pull/21107#issuecomment-4163506100
Follow-up to 5172ba5475 #21107

Closes #21181

.github/workflows/non-native.yml

@@ -349,7 +349,9 @@ jobs:
     steps:
       - name: 'install packages'
         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 "$HOME"/my-apt
+          printf "#!/bin/sh
+            while [ \$? = 0 ]; do for i in 1 2 3; do timeout 30 \"\$@\" && break 2; echo \"Error: slow server, retry \$i\"; sleep 1
+            dpkg --configure -a; done; false; done" > "$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)'