fix a few packaing issues after the rebase

Merge pull request #9673 from dotnet/insert-16.7

update 16.7 VS insertion target

fix sourcelink dependency in generated nuget package

Merge pull request fsharp#950 from baronfel/integrate-sourcelink

From dotnet/fsharp:079276b4b..37d0ccc.

This is a small bugfix release that I'm making primarily to publish a version of FCS with sourcelink enabled, so that tooling users can make use of that information.

Merge pull request #9436 from dotnet/merges/master-to-release/dev16.7

Merge master to release/dev16.7

bump version for packaging issues

Build Branch: release/dev16.6

Internal ID: fsharp-ci/20200417.4
Internal VS ID: rel.d16.6-30114.105

Merge pull request #9185 from dotnet/merges/master-to-release/fsharp5

Merge master to release/fsharp5

Merge pull request #8993 from dotnet/merges/master-to-release/fsharp5

Merge master to release/fsharp5

Build Branch: release/dev16.5

Internal ID: fsharp-ci/20200331.6
Internal VS ID: rel.d16.5-30002.166