Merge pull request #427 from AArnott/PinSdkVersion

Prefer modern UseDotNet task over obsolete DotNetCoreInstaller

Author: tonerdo

build.yml

@@ -1,7 +1,8 @@
 steps:
-- task: DotNetCoreInstaller@0
+- task: UseDotNet@2
   inputs:
-    version: '2.2.300'
-  displayName: 'Install .NET Core SDK'
+    version: 2.2.300
+  displayName: Install .NET Core SDK
+
 - script: dotnet msbuild build.proj /p:Configuration=$(buildConfiguration)
   displayName: 'Run Build'