If I build it by hand, works fine. Under synth it produces a version that uses wchar_t, whereas the library uses UTF-8.
I don't work with synth, but there are two CONFIGURE_ARGS:
--enable-utf8 use UTF-8 representation for strings (Unix only)
--enable-utf8only only support UTF-8 locales in UTF-8 build (Unix only)
Is this still relevant?