[CMake] No Warning when QtDialog isn't installed on Windows

[Miguel A. Figueroa-Villanueva]

Hello,

The following excerpt is taken from Source/QtDialog/CMakeLists.txt:

  # if qt is not static and we are on windows then skip the install
  # I don't want to distribute qt dlls
  IF(CMAKE_PACKAGE_QTGUI)
    INSTALL(TARGETS cmake-gui RUNTIME DESTINATION bin
    ${CMAKE_INSTALL_DESTINATION_ARGS})
  ENDIF(CMAKE_PACKAGE_QTGUI)

I would like to suggest adding a:

  MESSAGE(STATUS "WARNING: QtDialog will not be installed due to
distribution constraints.")

Or something like that. This is so that if someone requests to
BUILD_QtDialog, then he gets an appropriate warning. In my case, I was
building and installing cmake and QtDialog/cmake-gui silently failed
to install. Since there was a previous installation I was
inadvertently using the old QtDialog and new cmake...

Just my two cents.

--Miguel