[cmake] Update creation of object library dependencies for LINK_LIBS PUBLIC (v2)

[stephenneuendorffer]

Summary

REGEX matching doesn't work here because the problematic library can
sometimes be "-lpthread" and sometimes "pthread". Let's do the
simplest thing possible and just string compare.

llvm/cmake/modules/AddLLVM.cmake

if((ARG_SHARED AND ARG_STATIC) OR ARG_OBJECT)
     if(ARG_LINK_LIBS)
       cmake_parse_arguments(LINK_LIBS_ARG
         ""
         ""
         "PUBLIC;PRIVATE"
         ${ARG_LINK_LIBS})
       foreach(link_lib ${LINK_LIBS_ARG_PUBLIC})
         # Can't specify a dependence on -lpthread
-        if(NOT ${link_lib} MATCHES "-.*")
+        if(NOT ${link_lib} STREQUAL ${LLVM_PTHREAD_LIB})
           add_dependencies(${obj_name} ${link_lib})
         endif()
       endforeach()
     endif()
   endif()
 
   if(ARG_SHARED AND ARG_STATIC)
     # static