fix dotnet initialization on osx

azure-pipelines.yml

@@ -40,6 +40,11 @@ jobs:
       script: |
         dotnet tool install -g Cake.Tool --version 0.30.0
   - script: |
+      export COREHOST_TRACE=0
+      export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1
+      export DOTNET_CLI_TELEMETRY_OPTOUT=1
+      which dotnet
+      dotnet --info
       export PATH="$PATH:$HOME/.dotnet/tools"
       dotnet --info
       printenv