raise iOS deployment target to 12.0

CMakeLists.txt

@@ -171,7 +171,7 @@ endif()
 
 if(APPLE_IOS)
 	set(CMAKE_MACOSX_RPATH 1)
-	set(CMAKE_OSX_DEPLOYMENT_TARGET 10.0)
+	set(CMAKE_OSX_DEPLOYMENT_TARGET 12.0)
 
 	list(APPEND CMAKE_FIND_ROOT_PATH "${CMAKE_PREFIX_PATH}") # required for Boost
 	set(CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH FALSE)