fixed MacOS build

CMakeLists.txt

@@ -1,13 +1,14 @@
 cmake_minimum_required(VERSION 3.7)
 
+# https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_DEPLOYMENT_TARGET.html
+set(CMAKE_OSX_DEPLOYMENT_TARGET "10.7" CACHE STRING "Minimum OS X deployment version")
+
 project(VCVRack)
 
 set(CMAKE_CXX_STANDARD 14)
 
 set(RACK_APP rack)
 
-set(MAC_OS_VERSION_MIN "-mmacosx-version-min=10.7")
-
 set(RACK_GIT_REV "UNKNOWN")
 
 find_package(Git)
@@ -45,8 +46,8 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
    target_compile_definitions(${RACK_APP} PRIVATE ARCH_LIN)
    set_target_properties(${RACK_APP} PROPERTIES LINK_FLAGS -rdynamic)
 elseif (CMAKE_SYSTEM_NAME STREQUAL "Darwin")
-   target_compile_definitions(${RACK_APP} PRIVATE ARCH_MAC ${MAC_OS_VERSION_MIN})
-   set_target_properties(${RACK_APP} PROPERTIES LINK_FLAGS -export_dynamic "-undefined dynamic_lookup" ${MAC_OS_VERSION_MIN})
+   target_compile_definitions(${RACK_APP} PRIVATE ARCH_MAC)
+   set_target_properties(${RACK_APP} PROPERTIES LINK_FLAGS -export_dynamic "-undefined dynamic_lookup")
 endif ()
 
 target_include_directories(${RACK_APP} PRIVATE include)