Build broken with -Werror

[Tom de Vries]

Hi,

I'm running into:
...
elfnn-riscv.c: In function 'riscv_elf_additional_program_headers':
elfnn-riscv.c:5167:13: error: unused variable 's' [-Werror=unused-variable]
elfnn-riscv.c: In function 'riscv_elf_modify_segment_map':
elfnn-riscv.c:5179:32: error: unused parameter 'info'
[-Werror=unused-parameter]
...

I think this is due to:
...
commit fbc95f1e11facf233e89a9c2b4dde06b9aaf4b86
Author: Kito Cheng <kito.cheng@sifive.com>
Date:   Tue Jun 29 14:36:35 2021 +0800

    RISC-V: Add PT_RISCV_ATTRIBUTES and add it to PHDR.
...

Thanks,
- Tom