*.prelink.o is created when CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT
is enabled.

Replace $(linked-object) with $(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT)
so you will get a quick idea of when the --link option is passed.

No functional change is intended.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NJosh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14