Set macos deployment target in cmake list

relates to #1401

CMakeLists.txt

@@ -21,6 +21,7 @@ set(
 set(CMAKE_CXX_STANDARD 20 CACHE STRING "C++ standard")
 set(CMAKE_CXX_STANDARD_REQUIRED ON CACHE BOOL "Require C++ standard to be supported")
 set(CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "compile as PIC by default")
+set(CMAKE_OSX_DEPLOYMENT_TARGET "10.15" CACHE STRING "macos deployment target")
 
 option(HUNTER_ENABLED "Enable Hunter package manager" OFF)
 include("cmake/HunterGate.cmake")

toolchain.cmake

 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-set(CMAKE_OSX_DEPLOYMENT_TARGET 10.15)
\ No newline at end of file
+set(CMAKE_OSX_DEPLOYMENT_TARGET "10.15" CACHE STRING "macos deployment target")