Merge pull request microsoft#1523 from Milerius/patch-1

[MacOS]: fix wrong linking of Apple Frameworks

Author: barcharcraz

Release/src/CMakeLists.txt

@@ -94,7 +94,7 @@ endif()
 if(CPPREST_PPLX_IMPL STREQUAL "apple")
   find_library(COREFOUNDATION CoreFoundation "/")
   find_library(SECURITY Security "/")
-  target_link_libraries(cpprest PUBLIC ${COREFOUNDATION} ${SECURITY})
+  target_link_libraries(cpprest PRIVATE ${COREFOUNDATION} ${SECURITY})
   target_sources(cpprest PRIVATE pplx/pplxapple.cpp pplx/pplx.cpp pplx/threadpool.cpp ../include/pplx/threadpool.h)
   if(CPPREST_INSTALL_HEADERS)
     install(FILES ../include/pplx/threadpool.h DESTINATION include/pplx)