Previously only .nupkg files directly in the deps directory were copied.
This is a regression because it breaks `projectReferences = [ ... ];` in
buildDotnetModule.
A directory full of *.nupkg files is a valid nuget source. We do not need mono
and the Nuget command line tool to create this structure. This has two
advantages:
- Nuget is currently broken due to a kernel bug affecting mono (#229476).
Replacing the mkNugetSource implementation allows affected users on 6.1+
kernels compile .NET core packages again.
- It removes mono from the build closure of .NET core packages. .NET core
builds should not depend on .NET framework tools like mono.
There is no equivalent of the `nuget init` command in .NET core. The closest
command is `dotnet nuget push`, which just copies the *.nupkg files around
anyway, just like this PR does with `cp`.
`nuget init` used to extract the *.nuspec files from the nupkgs, this new
implementation doesn't. .NET core doesn't care, but it makes the license
extraction more difficult. What was previously done with find/grep/xml2 is now
a python script (extract-licenses-from-nupkgs.py).
This improves the metadata generation, previously it would take any
"license" entry from the nuspec, and tried to match it to an spdx ID from
"lib.licenses".
Sometimes however licenses are provided in plain-text, which we
obviously cannot cleanly resolve. This resulted in in useless information
("LICENSE.txt") being written to "meta.license".
Uses fsharp interactive (fsi) to run fsx script
Expose mkNugetSource and mkNugetDeps functions
Use them in writers.writeFSharp and buildDotnetModule
Add tests
