[libc] Collect objects only from visible deps of an object library.

[sivachandra]

Summary

A typo in an earlier change allowed this check to be missed.

libc/cmake/modules/LLVMLibCRules.cmake

function(add_object_library target_name)
   endif()
 
   set(all_object_files $<TARGET_OBJECTS:${target_name}>)
   if(ADD_OBJECT_DEPENDS)
     add_dependencies(
       ${target_name}
       ${ADD_OBJECT_DEPENDS}
     )
-    foreach(obj_target IN LISTS ADD_ENTRYPOINT_OBJ_SPECIAL_OBJECTS)
+    foreach(obj_target IN LISTS ADD_OBJECT_DEPENDS)
+      if(NOT TARGET ${obj_target})
+        # Not all targets will be visible. So, we will ignore those which aren't
+        # visible yet.
+        continue()
+      endif()
       get_target_property(obj_type ${obj_target} "TARGET_TYPE")
       if((NOT obj_type) OR (NOT (${obj_type} STREQUAL ${OBJECT_LIBRARY_TARGET_TYPE})))
         continue()
       endif()
       # If a dependency is also a object file library, we will collect the list of
       # object files from it.
       get_target_property(obj_files ${obj_target} "OBJECT_FILES")
       list(APPEND all_object_files ${obj_files})