Don't call into unsupported APIs on build targets which don't support quic

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -19,7 +19,6 @@
   <ItemGroup>
     <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.xml" />
   </ItemGroup>
-
   <ItemGroup>
     <Compile Include="System\Net\Http\ByteArrayContent.cs" />
     <Compile Include="System\Net\Http\ByteArrayHelpers.cs" />
@@ -662,20 +661,6 @@
   <ItemGroup Condition=" '$(TargetsBrowser)' == 'true'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Private.Runtime.InteropServices.JavaScript\src\System.Private.Runtime.InteropServices.JavaScript.csproj" />
   </ItemGroup>
-  <ItemGroup>
-    <Content Include="msquic.dll" Condition="Exists('msquic.dll')">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
-    </Content>
-    <Content Include="libmsquic.so" Condition="Exists('libmsquic.so')">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
-    </Content>
-    <Content Include="msquic.pdb" Condition="Exists('msquic.pdb')">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
-    </Content>
-  </ItemGroup>
   <ItemGroup>
     <None Include="Resources\SR.resx" />
   </ItemGroup>

src/libraries/System.Net.Http/tests/UnitTests/HttpClientTest.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.IO;
+using System.Reflection;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Net.Http.Tests
+{
+    public class HttpClientTest
+    {
+        [Fact]
+        public async Task GetAsync_Succeeds()
+        {
+            using var client = new HttpClient();
+            using var response = await client.GetAsync(Configuration.Http.RemoteServer);
+        }
+    }
+}

src/libraries/System.Net.Quic/src/ExcludeApiList.PNSE.txt

@@ -0,0 +1 @@
+T:System.Net.Quic.QuicImplementationProviders

src/libraries/System.Net.Quic/src/System.Net.Quic.csproj

@@ -7,8 +7,13 @@
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetsAnyOS)' == 'true'">SR.SystemNetQuic_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
+    <ApiExclusionListPath Condition="'$(TargetsAnyOS)' == 'true'">ExcludeApiList.PNSE.txt</ApiExclusionListPath>
   </PropertyGroup>
   <!-- Source files -->
+  <ItemGroup Condition="'$(TargetsAnyOS)' == 'true'">
+    <Compile Include="System\Net\Quic\Implementations\NoQuic\*.cs" />
+  </ItemGroup>
+  <!-- Source files -->
   <ItemGroup Condition="'$(TargetsAnyOS)' != 'true'">
     <Compile Include="System\Net\Quic\*.cs" />
     <Compile Include="System\Net\Quic\Implementations\*.cs" />

src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/NoQuic/NoQuicImplementationProvider.cs

@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Net.Quic.Implementations.NoQuic
+{
+    internal sealed class NoQuicImplementationProvider : QuicImplementationProvider
+    {
+        public override bool IsSupported => false;
+    }
+}

src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/NoQuic/QuicImplementationProviders.NoQuic.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Net.Quic
+{
+    public static partial class QuicImplementationProviders
+    {
+        public static Implementations.QuicImplementationProvider NoQuic { get; } = new Implementations.NoQuic.NoQuicImplementationProvider();
+        public static Implementations.QuicImplementationProvider Default => NoQuic;
+    }
+}

src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/QuicImplementationProvider.cs

@@ -11,8 +11,10 @@ internal QuicImplementationProvider() { }
 
         public abstract bool IsSupported { get; }
 
-        internal abstract QuicListenerProvider CreateListener(QuicListenerOptions options);
+        internal virtual QuicListenerProvider CreateListener(QuicListenerOptions options)
+            => throw new NotImplementedException();
 
-        internal abstract QuicConnectionProvider CreateConnection(QuicClientConnectionOptions options);
+        internal virtual QuicConnectionProvider CreateConnection(QuicClientConnectionOptions options)
+            => throw new NotImplementedException();
     }
 }