Do not float TFMs when building in non-source-only modes for tooling repos

[mmitche]

When building in non source-only modes, we should not float the TFMs for tooling repos. They should only use NetCurrent when building in source-only modes.

Evaluate which repos need this treatment and implement.

[ViktorHofer]

I think this is now implemented. MSBuild doesn't float anymore and other tooling repos shouldn't either.