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, 5 insertions, 0 deletions

diff --git a/Source/CPack/cmCPackGeneratorFactory.cxx b/Source/CPack/cmCPackGeneratorFactory.cxx
index 47e7527..a395a8f 100644
--- a/Source/CPack/cmCPackGeneratorFactory.cxx
+++ b/Source/CPack/cmCPackGeneratorFactory.cxx
@@ -15,6 +15,7 @@
 #include "cmCPackGenerator.h"
 #include "cmCPackLog.h"
 #include "cmCPackNSISGenerator.h"
+#include "cmCPackNuGetGenerator.h"
 #include "cmCPackSTGZGenerator.h"
 #include "cmCPackTGZGenerator.h"
 #include "cmCPackTXZGenerator.h"
@@ -105,6 +106,10 @@ cmCPackGeneratorFactory::cmCPackGeneratorFactory()
     this->RegisterGenerator("DEB", "Debian packages",
                             cmCPackDebGenerator::CreateGenerator);
   }
+  if (cmCPackNuGetGenerator::CanGenerate()) {
+    this->RegisterGenerator("NuGet", "NuGet packages",
+                            cmCPackNuGetGenerator::CreateGenerator);
+  }
 #ifdef __APPLE__
   if (cmCPackDragNDropGenerator::CanGenerate()) {
     this->RegisterGenerator("DragNDrop", "Mac OSX Drag And Drop",