Kevin Lalumiere f60b947e13
[vcpkg] Allow to use Nuget's cache for Nuget binary caching sources (fix #15169) (#15512)
* Fix warning on clang version 10.0.0-4ubuntu1

The warning was

```shell
../src/vcpkg/commands.porthistory.cpp:55:14: error: unused function 'is_date' [-Werror,-Wunused-function]
```

* Add environment variable VCPKG_USE_NUGET_CACHE

As the name suggests, this environment variable allow tu use Nuget
cache for Nuget binary caching sources.

* Document NuGet's Cache environment variable
2021-01-24 23:11:02 -08:00
..