Merge topic 'python-deployment-target'

771151ea

 python3: handle an unset deployment target
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !389

projects/apple-unix/python3.cmake

@@ -5,7 +5,7 @@ else ()
 endif ()
 
 set(python3_environment)
-if (APPLE)
+if (APPLE AND CMAKE_OSX_DEPLOYMENT_TARGET)
   list(APPEND python3_environment
     MACOSX_DEPLOYMENT_TARGET "${CMAKE_OSX_DEPLOYMENT_TARGET}")
 endif ()