CMakeLists: Link in system framework libraries explicitly on macOS

Makes our libraries explicitly link in which libraries they need.
This makes our dependencies explicit and removes the reliance on the
LIBS variable to contain the libraries that they need.

Source/Core/UICommon/CMakeLists.txt

@@ -9,9 +9,13 @@ add_library(uicommon
   VideoUtils.cpp
 )
 
-target_link_libraries(uicommon PUBLIC
+target_link_libraries(uicommon
+PUBLIC
   common
   cpp-optparse
+
+PRIVATE
+  $<$<BOOL:APPLE>:${IOK_LIBRARY}>
 )
 
 if(USE_X11)