Issues building net461 w/netstandard references on Mono; use net471 instead

Author: Sam Hanes

src/SqlClient.TestProjects/Lib/Lib.fsproj

@@ -3,7 +3,7 @@
   <Import Project="..\..\..\fsc.props" />
   <Import Project="..\..\..\netfx.props" />
   <PropertyGroup>
-    <TargetFrameworks>net461;netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>net471;netcoreapp2.0</TargetFrameworks>
     <AssemblyName>Lib</AssemblyName>
     <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
@@ -18,6 +18,7 @@
     <Content Include="packages.config" />
   </ItemGroup>
   <ItemGroup>
+    <Reference Include="netstandard" />
     <Reference Include="FSharp.Data.SqlClient">
       <HintPath>..\..\..\bin\netstandard2.0\FSharp.Data.SqlClient.dll</HintPath>
     </Reference>