2a0c747bc0
Submodule local/sources/relibc updated to 688e76ca, which clarifies
the misleading 'riscv64 and x86' message on the cfg-gated
unimplemented!() in do_tlsdesc_reloc. The gate correctly excludes
x86_64 and aarch64; the message now matches the actual reach (only
riscv64 fires).