Temporarily change tfm to netstandard1.3

Ideally we want to target netstandard2.0 but this conversion is blocked on the issue: https://github.com/dotnet/sdk/issues/1219

build/dependencies.props

@@ -1,6 +1,7 @@
 <Project>
   <PropertyGroup>
     <AspNetCoreVersion>2.0.0-*</AspNetCoreVersion>
+    <CoreFxVersion>4.3.0</CoreFxVersion>
     <InternalAspNetCoreSdkVersion>2.1.0-*</InternalAspNetCoreSdkVersion>
     <JsonNetVersion>10.0.1</JsonNetVersion>
     <MoqVersion>4.7.1</MoqVersion>

src/Microsoft.AspNetCore.JsonPatch/Microsoft.AspNetCore.JsonPatch.csproj

@@ -3,13 +3,15 @@
 
   <PropertyGroup>
     <Description>ASP.NET Core support for JSON PATCH.</Description>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netstandard1.3</TargetFramework>
     <NoWarn>$(NoWarn);CS1591</NoWarn>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageTags>aspnetcore;json;jsonpatch</PackageTags>
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.CSharp" Version="$(CoreFxVersion)" />
+    <PackageReference Include="System.Reflection.TypeExtensions" Version="$(CoreFxVersion)" />
     <PackageReference Include="Newtonsoft.Json" Version="$(JsonNetVersion)" />
     <PackageReference Include="Microsoft.Extensions.ClosedGenericMatcher.Sources" Version="$(AspNetCoreVersion)" PrivateAssets="All" />
   </ItemGroup>

test/Microsoft.AspNetCore.JsonPatch.Test/Microsoft.AspNetCore.JsonPatch.Test.csproj

@@ -3,7 +3,8 @@
   <Import Project="..\..\build\common.props" />
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFrameworks>netcoreapp2.0;net461</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">netcoreapp2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>