Don't re-specify default included refs, include net48 in test targets

Author: nblumhardt

src/Serilog.Sinks.Async/Serilog.Sinks.Async.csproj

@@ -33,16 +33,6 @@
     <PackageReference Include="Nullable" Version="1.3.1" PrivateAssets="all" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net471' ">
-    <Reference Include="System" />
-    <Reference Include="Microsoft.CSharp" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
-    <Reference Include="System" />
-    <Reference Include="Microsoft.CSharp" />
-  </ItemGroup>
-
   <ItemGroup>
     <None Include="..\..\assets\serilog-sink-nuget.png" Pack="true" Visible="false" PackagePath="/" />
     <None Include="..\..\README.md" Pack="true" Visible="false" PackagePath="/" />

test/Serilog.Sinks.Async.PerformanceTests/Serilog.Sinks.Async.PerformanceTests.csproj

@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT'">net48</TargetFrameworks>
+    <TargetFrameworks>$(TargetFrameworks);net6.0;net8.0</TargetFrameworks>
     <AssemblyOriginatorKeyFile>../../assets/Serilog.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>

test/Serilog.Sinks.Async.Tests/Serilog.Sinks.Async.Tests.csproj

@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT'">net48</TargetFrameworks>
+    <TargetFrameworks>$(TargetFrameworks);net6.0;net8.0</TargetFrameworks>
     <AssemblyOriginatorKeyFile>../../assets/Serilog.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>