setup build failure

[Ken Brown]

The current setup sources fail to build because ~StringChoiceOption is not defined:

   CXXLD    setup.exe
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
io_stream_cygfile.o:/home/kbrown/src/cygsetup/x86_64/../setup/io_stream_cygfile.cc:40: 
undefined reference to `StringChoiceOption::~StringChoiceOption()'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
io_stream_cygfile.o:/home/kbrown/src/cygsetup/x86_64/../setup/io_stream_cygfile.cc:43: 
undefined reference to 
`StringChoiceOption::StringChoiceOption(std::vector<std::pair<char const*, int>, 
std::allocator<std::pair<char const*, int> > >, char, char const*, 
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > 
const&, bool, int, int)'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
main.o:/home/kbrown/src/cygsetup/x86_64/../setup/main.cc:107: undefined 
reference to `StringChoiceOption::~StringChoiceOption()'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
main.o:/home/kbrown/src/cygsetup/x86_64/../setup/main.cc:107: undefined 
reference to `StringChoiceOption::StringChoiceOption(std::vector<std::pair<char 
const*, int>, std::allocator<std::pair<char const*, int> > >, char, char const*, 
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > 
const&, bool, int, int)'
collect2: error: ld returned 1 exit status

Ken