Build fails due to undefined references to libsframe and libzstd

[cvonelm]

It appears that libbfd started to require libsframe and libzstd:

[ 21%] Linking CXX executable lo2s
/usr/bin/ld: /usr/lib/libbfd.a(elfxx-x86.o): in function `_bfd_x86_elf_write_sframe_plt.isra.0':
(.text+0xeaa): undefined reference to `sframe_encoder_write'
/usr/bin/ld: (.text+0xee2): undefined reference to `sframe_encoder_free'
/usr/bin/ld: /usr/lib/libbfd.a(elfxx-x86.o): in function `_bfd_x86_elf_create_sframe_plt.isra.0':
(.text+0xfe7): undefined reference to `sframe_encode'
/usr/bin/ld: (.text+0xff8): undefined reference to `sframe_calc_fre_type'
/usr/bin/ld: (.text+0x1004): undefined reference to `sframe_fde_create_func_info'
/usr/bin/ld: (.text+0x1019): undefined reference to `sframe_encoder_add_funcdesc'
/usr/bin/ld: (.text+0x1067): undefined reference to `sframe_encoder_add_fre'
/usr/bin/ld: (.text+0x10cf): undefined reference to `sframe_encode'
/usr/bin/ld: (.text+0x10e0): undefined reference to `sframe_calc_fre_type'
/usr/bin/ld: (.text+0x10ec): undefined reference to `sframe_fde_create_func_info'
/usr/bin/ld: (.text+0x1158): undefined reference to `sframe_encode'
/usr/bin/ld: (.text+0x1169): undefined reference to `sframe_calc_fre_type'
/usr/bin/ld: (.text+0x1175): undefined reference to `sframe_fde_create_func_info'
/usr/bin/ld: (.text+0x1194): undefined reference to `sframe_fde_create_func_info'
/usr/bin/ld: (.text+0x11ae): undefined reference to `sframe_encoder_add_funcdesc'
/usr/bin/ld: (.text+0x11f6): undefined reference to `sframe_encoder_add_fre'
/usr/bin/ld: (.text+0x124f): undefined reference to `sframe_encode'
/usr/bin/ld: /usr/lib/libbfd.a(elf-sframe.o): in function `_bfd_elf_parse_sframe':
(.text+0x13d): undefined reference to `sframe_decode'
/usr/bin/ld: (.text+0x157): undefined reference to `sframe_decoder_get_num_fidx'
/usr/bin/ld: (.text+0x287): undefined reference to `sframe_decoder_free'
/usr/bin/ld: /usr/lib/libbfd.a(elf-sframe.o): in function `_bfd_elf_discard_section_sframe':
(.text+0x2ec): undefined reference to `sframe_decoder_get_num_fidx'
/usr/bin/ld: /usr/lib/libbfd.a(elf-sframe.o): in function `_bfd_elf_merge_section_sframe':
(.text+0x757): undefined reference to `sframe_decoder_get_abi_arch'
/usr/bin/ld: (.text+0x762): undefined reference to `sframe_encoder_get_abi_arch'
/usr/bin/ld: (.text+0x778): undefined reference to `sframe_decoder_get_num_fidx'
/usr/bin/ld: (.text+0x787): undefined reference to `sframe_encoder_get_num_fidx'
/usr/bin/ld: (.text+0x818): undefined reference to `sframe_decoder_get_funcdesc'
/usr/bin/ld: (.text+0x869): undefined reference to `sframe_decoder_get_hdr_size'
/usr/bin/ld: (.text+0x8f2): undefined reference to `sframe_encoder_add_funcdesc'
/usr/bin/ld: (.text+0x92d): undefined reference to `sframe_decoder_get_fre'
/usr/bin/ld: (.text+0x945): undefined reference to `sframe_encoder_add_fre'
/usr/bin/ld: (.text+0x98d): undefined reference to `sframe_decoder_free'
/usr/bin/ld: (.text+0xb85): undefined reference to `sframe_decoder_get_abi_arch'
/usr/bin/ld: (.text+0xb96): undefined reference to `sframe_decoder_get_fixed_fp_offset'
/usr/bin/ld: (.text+0xba6): undefined reference to `sframe_decoder_get_fixed_ra_offset'
/usr/bin/ld: (.text+0xbcc): undefined reference to `sframe_encode'
/usr/bin/ld: /usr/lib/libbfd.a(elf-sframe.o): in function `_bfd_elf_write_section_sframe':
(.text+0xc89): undefined reference to `sframe_encoder_write'
/usr/bin/ld: (.text+0xcb7): undefined reference to `sframe_encoder_free'
/usr/bin/ld: /usr/lib/libbfd.a(compress.o): in function `decompress_contents':
(.text+0x196): undefined reference to `ZSTD_decompress'
/usr/bin/ld: (.text+0x19f): undefined reference to `ZSTD_isError'
/usr/bin/ld: /usr/lib/libbfd.a(compress.o): in function `bfd_compress_section_contents':
(.text+0x1338): undefined reference to `ZSTD_compress'
/usr/bin/ld: (.text+0x1346): undefined reference to `ZSTD_isError'

[cvonelm]

The easiest solution, I think, would be checking whether libsframe exists, and if it exists linking to both libsframe and libzstd. Both new dependencies appear to arrived in the 2.40 release of binutils.

The only problem I have spotted, at least on my system, is that there is no static libzstd, so we might need to change the default lo2s_USE_STATIC_LIBS=MOSTLY build option to link binutils dynamically.