CPack: Add NuGet support

Create a CPack generator that uses `nuget.exe` to create packages:

    https://docs.microsoft.com/en-us/nuget/what-is-nuget

NuGet packages could be easily produced from a `*.nuspec` file (running
`nuget pack` in the directory w/ the spec file).  The spec filename does
not affect the result `*.nupkg` name -- only `id` and `version` elements
of the spec are used (by NuGet).

Some implementation details:

* Minimize C++ code -- use CMake script do to the job. It just let the
  base class (`cmCPackGenerator`) to preinstall everything to a temp
  directory, render the spec file and run `nuget pack` in it, harvesting
  `*.nupkg` files...;

* Ignore package name (and use default paths) prepared by the base class
  (only `CPACK_TEMPORARY_DIRECTORY` is important) -- final package
  filename is a responsibility of NuGet, so after generation just scan the
  temp directory for the result `*.nupkg` file(s) and update
  `packageFileNames` data-member of the generator;

* The generator supports _all-in-one_ (default), _one-group-per-package_
  and _one-component-per-package_ modes.

1 files changed, 12 insertions, 0 deletions

diff --git a/Tests/CPackComponentsForAll/RunCPackVerifyResult.cmake b/Tests/CPackComponentsForAll/RunCPackVerifyResult.cmake
index 2bfb5b0..253d128 100644
--- a/Tests/CPackComponentsForAll/RunCPackVerifyResult.cmake
+++ b/Tests/CPackComponentsForAll/RunCPackVerifyResult.cmake
@@ -70,6 +70,18 @@ elseif(CPackGen MATCHES "DEB")
     elseif(${CPackComponentWay} STREQUAL "AllInOne")
         set(expected_count 1)
     endif()
+elseif(CPackGen MATCHES "NuGet")
+    set(config_verbose -D "CPACK_NUGET_PACKAGE_DEBUG=1")
+    set(expected_file_mask "${CPackComponentsForAll_BINARY_DIR}/MyLib*1.0.2.nupkg")
+    if(${CPackComponentWay} STREQUAL "default")
+        set(expected_count 1)
+    elseif(${CPackComponentWay} STREQUAL "OnePackPerGroup")
+        set(expected_count 3)
+    elseif(${CPackComponentWay} STREQUAL "IgnoreGroup")
+        set(expected_count 4)
+    elseif(${CPackComponentWay} STREQUAL "AllInOne")
+        set(expected_count 1)
+    endif()
 endif()
 
 if(CPackGen MATCHES "DragNDrop")