[cpack_installer] reworked how packaging is enabled for windows

cmake/Platform/Windows/Packaging_windows.cmake

@@ -9,17 +9,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #
 
-set(LY_WIX_PATH "" CACHE PATH "Path to the WiX install path")
-
-if(LY_WIX_PATH)
-    file(TO_CMAKE_PATH ${LY_WIX_PATH} CPACK_WIX_ROOT)
-elseif(DEFINED ENV{WIX})
-    file(TO_CMAKE_PATH $ENV{WIX} CPACK_WIX_ROOT)
-endif()
+set(CPACK_WIX_ROOT "" CACHE PATH "Path to the WiX install path")
 
 if(CPACK_WIX_ROOT)
     if(NOT EXISTS ${CPACK_WIX_ROOT})
-        message(FATAL_ERROR "Invalid path supplied for LY_WIX_PATH argument or WIX environment variable")
+        message(FATAL_ERROR "Invalid path supplied for CPACK_WIX_ROOT argument")
     endif()
 else()
     # early out as no path to WiX has been supplied effectively disabling support