LLD reports bogus warnings when linking the kernel

When linking the kernel (5.10) with Morello LLD, I get a lot of warnings from unresolved references to weak symbols, for instance:

ld.lld: warning: DynsymIndex == 0 for R_AARCH64_GLOB_DAT relocation against weak <undefined> (in GOT) kallsyms_num_syms+0
...
ld.lld: warning: DynsymIndex == 0 for R_AARCH64_ABS64 relocation against weak <undefined> efi_attr_runtime+0

Note that no Morello code is involved here; this can be reproduced by building the vanilla 5.10 kernel: those warnings are issued with Morello LLVM, while no warning is printed with upstream LLVM (everything else being the same).