Use -exported_symbol on macOS

[cho-m]

--version-script is not supported on macOS ld while -export-symbols-regex seems to be specific to libtool. Previous macOS ld may have skipped this but Xcode 16 fails:

clang: error: unknown argument: '-export-symbols-regex=^jose_.*'

macOS instead has:

• -exported_symbol <symbol>
• -exported_symbols_list <filename>

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Could alternatively use -exported_symbols_list and hardcode every name similar to libjose.map, but there is a good chance of it going out-of-sync without proper checks as it needs a different file with a flat list of symbols/patterns

May want to consider using visibility attributes instead which should allow better cross-compatibility.

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The build failure was seen in Homebrew when trying to build jose on Sequoia (Xcode 16, based on LLVM 17).

Taking a look at binaries built from older Xcode, the flags were most likely never used, e.g.

❯ nm -gU lib/libjose.dylib | grep -v jose
0000000000010ad6 T _add_entity
000000000001090b T _bn_decode
0000000000010917 T _bn_decode_json
000000000001099a T _bn_encode
0000000000010a26 T _bn_encode_json
0000000000010d3d T _copy_val
0000000000005810 T _encode_protected
0000000000005891 T _handle_zip_enc
0000000000006b84 T _hsh
0000000000006d03 T _hsh_buf
0000000000006ccd T _hsh_io
0000000000010810 T _str2enum
0000000000005886 T _zero
0000000000005997 T _zip_in_protected_header

❯ nm -gU lib/libjose.dylib | grep jose | wc -l
      59

Doing a build with -exported_symbol

❯ nm -gU lib/libjose.dylib | grep -v jose

❯ nm -gU lib/libjose.dylib | grep jose | wc -l
      59