switching from MSBuild to .NET Core SDK builds

Author: salaros

appveyor.yml

@@ -83,12 +83,12 @@ assembly_info:
 
 # Run scripts below before
 before_build:
-  - where msbuild
-  - cmd: msbuild /t:Clean
+  - where dotnet
+  - cmd: dotnet clean
 
 # To run your custom scripts instead of automatic MSBuild
 build_script:
-  - cmd: msbuild /t:Rebuild /p:Configuration=Debug
+  - cmd: dotnet build --configuration Debug
 
 # NuGet files qualified as artifacts
 artifacts: