[CMake] Solution folder property does not work for external projects in cmake 2.8.3

[Jens Auer]

Hi,

I just downloaded the new cmake 2.8.3 release and found a bug. We
include several external VC++ projects in our solution and group them
into folders using the old SOLUTION_FOLDER patch. When I checked the new
property FOLDER in cmake 2.8.3, it turns out that it works for all
projects except those included by include_external_msproject. When you
modify the following example to point to an existing .vcproj-file and
open the generated solution in visual studio 2005, only the custom
target will be found in folder1/folder2:

set_property(GLOBAL PROPERTY USE_FOLDERS On)
cmake_minimum_required(VERSION 2.8.3)
project(project)
include_external_msproject(externalProject
<PATH_TO_SOME_EXTERNAL_VCPROJ_FILE>)
set_target_properties(externalProject PROPERTIES FOLDER folder1/folder2)
add_custom_target(infolder)
set_target_properties(infolder PROPERTIES FOLDER folder1/folder2)

I also had to put the set_property in the first line of the file to
activate solution folders support, setting it after the
cmake_minimum_required did not turn the support on. I don't know if this
is intended or not.

Best regards,
  Jens