Ubuntu package dotnet-sdk-10.0 uninstalls earlier .NET runtimes

... and the install is rather slow, so try a different approach.

Author: stakx

appveyor.yml

@@ -20,7 +20,9 @@ for:
 
   # install .NET 10 SDK
   install:
-  - sudo apt-get update && sudo apt-get install -y dotnet-sdk-10.0
+  - curl -L https://dot.net/v1/dotnet-install.sh -o dotnet-install.sh
+  - chmod +x ./dotnet-install.sh
+  - sudo ./dotnet-install.sh --channel 10.0
 
   # build and run tests
   build_script: