chore(ci): try to make sysroot step more reliable (#17383)
Main is failing a lot because of:
```
Err:8 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 debootstrap all 1.0.118ubuntu1.8
Connection failed [IP: 40.81.13.82 80]
Fetched 44.1 MB in 60s (734 kB/s)
E: Failed to fetch http://azure.archive.ubuntu.com/ubuntu/pool/main/d/debootstrap/debootstrap_1.0.118ubuntu1.8_all.deb Connection failed [IP: 40.81.13.82 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
```
