Add CurrentLtsTargetFramework only when it's not present (#61076)

Author: BrennanConroy

src/Caching/StackExchangeRedis/src/Microsoft.Extensions.Caching.StackExchangeRedis.csproj

@@ -2,7 +2,8 @@
 
   <PropertyGroup>
     <Description>Distributed cache implementation of Microsoft.Extensions.Caching.Distributed.IDistributedCache using Redis.</Description>
-    <TargetFrameworks>$(DefaultNetCoreTargetFramework);$(DefaultNetFxTargetFramework);netstandard2.0;$(CurrentLtsTargetFramework)</TargetFrameworks>
+    <TargetFrameworks>$(DefaultNetCoreTargetFramework);$(DefaultNetFxTargetFramework);netstandard2.0</TargetFrameworks>
+    <TargetFrameworks Condition="! $(TargetFrameworks.Contains('$(CurrentLtsTargetFramework)'))">$(TargetFrameworks);$(CurrentLtsTargetFramework)</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageTags>cache;distributedcache;redis</PackageTags>
     <ExcludeFromSourceOnlyBuild>true</ExcludeFromSourceOnlyBuild>

src/Servers/Connections.Abstractions/src/Microsoft.AspNetCore.Connections.Abstractions.csproj

@@ -2,7 +2,8 @@
 
   <PropertyGroup>
     <Description>Core components of ASP.NET Core networking protocol stack.</Description>
-    <TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;netstandard2.1;$(DefaultNetCoreTargetFramework);$(CurrentLtsTargetFramework)</TargetFrameworks>
+    <TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;netstandard2.1;$(DefaultNetCoreTargetFramework)</TargetFrameworks>
+    <TargetFrameworks Condition="! $(TargetFrameworks.Contains('$(CurrentLtsTargetFramework)'))">$(TargetFrameworks);$(CurrentLtsTargetFramework)</TargetFrameworks>
     <TargetFrameworks Condition="'$(DotNetBuildSourceOnly)' == 'true'">$(DefaultNetCoreTargetFramework)</TargetFrameworks>
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>