build: use osx target 10.15 for Qt6 on Mac [skip ci] (#451)

CMakeLists.txt

@@ -80,10 +80,6 @@ if(NOT
   set(ICON_FILE ${CMAKE_CURRENT_SOURCE_DIR}/Resources/${ICON_NAME})
 endif()
 
-if(APPLE)
-  set(CMAKE_OSX_DEPLOYMENT_TARGET 10.14)
-endif()
-
 if(MSVC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.14)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /experimental:external /external:W0 ")
   set(CMAKE_INCLUDE_SYSTEM_FLAG_CXX "/external:I ")
@@ -197,6 +193,15 @@ set(KLOGG_QT_VERSION ${Qt${QT_VERSION_MAJOR}Core_VERSION})
 message("Qt version ${KLOGG_QT_VERSION}")
 message("LTO ${KLOGG_USE_LTO}")
 
+if(APPLE)
+  if(${QT_VERSION_MAJOR} STREQUAL "6")
+    set(CMAKE_OSX_DEPLOYMENT_TARGET 10.15)
+  else()
+    set(CMAKE_OSX_DEPLOYMENT_TARGET 10.14)
+  endif()
+  message("OSX target ${CMAKE_OSX_DEPLOYMENT_TARGET}")
+endif()
+
 set(CMAKE_AUTOMOC OFF)
 set(CMAKE_INCLUDE_CURRENT_DIR OFF)
 set(BUILD_SHARED_LIBS OFF)