Fix cross-compiling between i686 and x86_64 when building SHARED lib.

Credits goes to alexrass.

Source/CMake/Modules/Urho3D-CMake-common.cmake

@@ -261,9 +261,11 @@ else ()
             if (URHO3D_64BIT)
                 set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -m64")
                 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m64")
+                set (CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -m64")
             else ()
                 set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -m32")
                 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32")
+                set (CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -m32")
                 if (URHO3D_SSE)
                     if (NOT WIN32)
                         set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -msse")