build: update corert compiler (#6485)

frameworks/CSharp/aspnetcore-corert/PlatformBenchmarks/PlatformBenchmarks.csproj

@@ -8,6 +8,7 @@
     <!-- Opt out of the "easy mode" of the CoreRT compiler (http://aka.ms/OptimizeCoreRT) -->
     <TrimMode>link</TrimMode>
     <IlcGenerateStackTraceData>false</IlcGenerateStackTraceData>
+    <IlcOptimizationPreference>Speed</IlcOptimizationPreference>
   </PropertyGroup>
   
   <ItemGroup>
@@ -20,6 +21,6 @@
 
   <ItemGroup>
     <PackageReference Include="Utf8Json" Version="1.3.7" />
-    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="6.0.0-alpha.*" />
+    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="6.0.0-*" />
   </ItemGroup>
 </Project>