When Clang LTO is enabled, vmlinux_link() reuses vmlinux.o instead of
re-linking ${KBUILD_VMLINUX_OBJS} and ${KBUILD_VMLINUX_LIBS}.

That is the only difference here, so merge the similar code.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>