Csc/Vbc Tasks should log stderr as error (#27349)

src/Compilers/Core/MSBuildTask/ManagedCompiler.cs

@@ -34,6 +34,10 @@ static ManagedCompiler()
         public ManagedCompiler()
         {
             TaskResources = ErrorString.ResourceManager;
+
+            // If there is a crash, the runtime error is output to stderr and
+            // we want MSBuild to print it out regardless of verbosity.
+            LogStandardErrorAsError = true;
         }
 
         #region Properties