Restore empty dependency target for net452 in xunit.assert.nuspec

Author: bradwilson

src/Directory.Build.props

@@ -14,7 +14,7 @@
     <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
     <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
     <LangVersion>latest</LangVersion>
-    <NoWarn>$(NoWarn);NU1603;NU5131;CS1701</NoWarn>
+    <NoWarn>$(NoWarn);NU1603;NU5128;NU5131;CS1701</NoWarn>
     <PackageId>$(MSBuildProjectName)</PackageId>
     <RootNamespace>Xunit</RootNamespace>
     <SignAssembly>true</SignAssembly>

src/xunit.assert.nuspec

@@ -13,6 +13,7 @@
     <copyright>Copyright (C) .NET Foundation</copyright>
     <repository type="git" url="https://github.com/xunit/xunit" commit="$GitCommitId$" />
     <dependencies>
+      <group targetFramework="net452" />
       <group targetFramework="netstandard1.1">
         <dependency id="NETStandard.Library" version="1.6.1" />
       </group>