Disable compiler warnings during component discovery phase

Author: chsienki

src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.Component.targets

@@ -244,7 +244,7 @@ Copyright (c) .NET Foundation. All rights reserved.
          UseSharedCompilation="$(UseSharedCompilation)"
          Utf8Output="$(Utf8Output)"
          VsSessionGuid="$(VsSessionGuid)"
-         WarningLevel="$(WarningLevel)"
+         WarningLevel="0"
          WarningsAsErrors="$(WarningsAsErrors)"
          WarningsNotAsErrors="$(WarningsNotAsErrors)"
          PathMap="$(PathMap)"