It depends on what exactly you need.
Currently new build infrastructure is being developed that should allow you to build many .NET Framework libraries and console applications on every platform that .NET Core supports.
See the design PR for Easy Acquisition of .NET Framework Targeting Pack which describes the packages currently in preview which can be used in a project via
<PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies"
Version="1.0.0-preview.1"
PrivateAssets="All" />
Another option would be to install mono and use mono's msbuild
command to build existing .NET Framework projects, although there may be some different in regard to assembly resolution when using specific NuGet packages.
However, there is no tooling for more advanced scenarios like WPF or ASP.NET (classic) applications as well as EF 6 .edmx tooling.