Fix a problem building MSI using localized (Spanish) Visual Studio 2010.

VS did not like to execute 2 commands in custom build step, workaround is 
to use single COMMAND instead of 2.

win/packaging/CMakeLists.txt

@@ -157,7 +157,6 @@ ENDIF()
 
 ADD_CUSTOM_TARGET(
   MSI
-  COMMAND set VS_UNICODE_OUTPUT=
   COMMAND ${CMAKE_COMMAND} 
   ${CONFIG_PARAM} 
   -P  ${CMAKE_CURRENT_BINARY_DIR}/create_msi.cmake
@@ -166,7 +165,6 @@ ADD_DEPENDENCIES(MSI wixca)
 
 ADD_CUSTOM_TARGET(
   MSI_ESSENTIALS
-  COMMAND set VS_UNICODE_OUTPUT=
   COMMAND ${CMAKE_COMMAND} -DESSENTIALS=1 
   ${CONFIG_PARAM}
   -P  ${CMAKE_CURRENT_BINARY_DIR}/create_msi.cmake

win/packaging/create_msi.cmake.in

@@ -28,7 +28,7 @@ SET(THIRD_PARTY_DOWNLOAD_LOCATION "@THIRD_PARTY_DOWNLOAD_LOCATION@")
 SET(THIRD_PARTY_FEATURE_CONDITION "@THIRD_PARTY_FEATURE_CONDITION@")
 SET(LIBMYSQL_LOCATION "@LIBMYSQL_LOCATION@")
 
-
+SET($ENV{VS_UNICODE_OUTPUT} "")
 IF(LIBMYSQL_LOCATION AND CMAKE_CFG_INTDIR) 
  # resolve libmysql full path
  STRING(REPLACE "${CMAKE_CFG_INTDIR}" "${CMAKE_INSTALL_CONFIG_NAME}" LIBMYSQL_LOCATION "${LIBMYSQL_LOCATION}")