guix: re-enable exported symbol checking for RISC-V

[fanquake]

This is currently disabled, when it can likely be fixed and re-enabled:

bitcoin/contrib/devtools/symbol-check.py

Line 210 in 673acab

if binary.header.machine_type == lief.ELF.ARCH.RISCV or name in IGNORE_EXPORTS:

A Guix build with the exception dropped shows there are symbols being exported in the RISC-V bins:

/opt/homebrew/opt/binutils/bin/objdump -T bitcoind

0000000000080500  w   DF .text	00000000000000a6  Base        _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC1IS3_EEPKcRKS3_
000000000007f6a0  w   DF .text	0000000000000064  Base        _ZNSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEED1Ev
000000000007e9da  w   DF .text	0000000000000024  Base        _ZNKSt5ctypeIcE8do_widenEc

std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string<std::allocator<char> >(char const*, std::allocator<char> const&)
std::__cxx11::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::~basic_stringbuf()
std::ctype<char>::do_widen(char) const

[hebasto]

Historically, symbol checking for RISC-V was skipped from the beginning for the following reason:

Need to skip RISC-V for now, the linker would export so many symbols.

[fanquake]

I don't think that's relevant anymore? I've listed the exported symbols above. It's 3.

[laanwj]

i'll try to figure out why it exports those three symbols, and if it is indication of a problem, and if not, add them to the exceptions

demangled, these are:

std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string<std::allocator<char> >(char const*, std::allocator<char> const&)
std::__cxx11::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::~basic_stringbuf()
std::ctype<char>::do_widen(char) const

[laanwj]

Holding this off until #29987 is.merged.