Add a test confirming that X509Certificate is trimmed

...when using `CreateSlimBuilder`.

Author: amcasey

src/DefaultBuilder/test/Microsoft.AspNetCore.NativeAotTests/Microsoft.AspNetCore.NativeAotTests.proj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <ItemGroup>
+    <TestConsoleAppSourceFiles Include="SlimBuilderDoesNotDependOnX509Test.cs" />
     <TestConsoleAppSourceFiles Include="UseStartupThrowsForStructContainersTest.cs" />
   </ItemGroup>
 

src/DefaultBuilder/test/Microsoft.AspNetCore.NativeAotTests/SlimBuilderDoesNotDependOnX509Test.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Reflection;
+using Microsoft.AspNetCore.Builder;
+
+#nullable enable
+
+var builder = WebApplication.CreateSlimBuilder(args);
+_ = builder.Build();
+
+if (GetType("System.Security.Cryptography", "System.Security.Cryptography.X509Certificates.X509Certificate") is not null) {
+    return 1;
+}
+
+return 100; // Success
+
+[UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode",
+    Justification = "Returning null when the type is unreferenced is desirable")]
+static Type? GetType(string assemblyName, string typeName) {
+    var assembly = AppDomain.CurrentDomain.GetAssemblies().SingleOrDefault(a => a.GetName().Name == assemblyName);
+    return assembly?.GetType(typeName);
+}