Use setup-nuget to fix broken nuget in GitHub actions

[tautschnig]

All Windows builds were failing to download clcache from nuget. This
problem also documented in
actions/runner-images#3240. Follow
their approach to fix the nuget setup.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[NlightNFotis]

Hi Michael, thanks for this 👍🏻 I was also playing around with Nuget locally and I got the install instructions from CI working on my machine, which made it all the more confusing (same version 5.9.1)

[tautschnig]

Hi Michael, thanks for this 👍🏻 I was also playing around with Nuget locally and I got the install instructions from CI working on my machine, which made it all the more confusing (same version 5.9.1)

I was lazy and started digging through https://github.com/actions/virtual-environments/issues with the hope that we're not the only ones facing the problem :-)