Added support for .NET Framework 4.7.1 and .NET Standard 2.0.

Author: konard

Platform.RegularExpressions.Transformer.CSharpToCpp.Tests/Platform.RegularExpressions.Transformer.CSharpToCpp.Tests.csproj

@@ -1,11 +1,15 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.0</TargetFramework>
+    <TargetFrameworks>net471;netcoreapp2.1;netcoreapp3.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>
 
+  <ItemGroup Condition="$(TargetFramework.StartsWith('net4')) AND '$(MSBuildRuntimeType)' == 'Core' AND '$(OS)' != 'Windows_NT'">
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="All" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.3.0" />
     <PackageReference Include="xunit" Version="2.4.1" />

Platform.RegularExpressions.Transformer.CSharpToCpp/Platform.RegularExpressions.Transformer.CSharpToCpp.csproj

@@ -6,7 +6,7 @@
     <AssemblyTitle>Platform.RegularExpressions.Transformer.CSharpToCpp</AssemblyTitle>
     <VersionPrefix>0.0.8</VersionPrefix>
     <Authors>Konstantin Diachenko</Authors>
-    <TargetFramework>netstandard2.1</TargetFramework>
+    <TargetFrameworks>net471;netstandard2.0;netstandard2.1</TargetFrameworks>
     <AssemblyName>Platform.RegularExpressions.Transformer.CSharpToCpp</AssemblyName>
     <PackageId>Platform.RegularExpressions.Transformer.CSharpToCpp</PackageId>
     <PackageTags>LinksPlatform;RegularExpressions.Transformer.CSharpToCpp;CSharpToCppTransformer</PackageTags>
@@ -27,8 +27,12 @@
     <PackageReleaseNotes>SourceLink enabled.</PackageReleaseNotes>
   </PropertyGroup>
 
+  <ItemGroup Condition="$(TargetFramework.StartsWith('net4')) AND '$(MSBuildRuntimeType)' == 'Core' AND '$(OS)' != 'Windows_NT'">
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="All" />
+  </ItemGroup>
+
   <ItemGroup>
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19367-01" PrivateAssets="All"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19367-01" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup>