Fails to build with clang

EquationTags.cc:74:14: error: invalid operands to binary expression ('std::ostream' (aka 'basic_ostream<char>') and 'const char [3]')
      output << "  " << eqn + 1
      ~~~~~~ ^  ~~~~
/usr/include/c++/v1/cstddef:141:3: note: candidate function template not viable: cannot convert argument of incomplete type 'std::ostream' (aka 'basic_ostream<char>') to 'std::byte' for 1st argument
  operator<< (byte  __lhs, _Integer __shift) noexcept
  ^
/usr/include/c++/v1/memory:3983:1: note: candidate template ignored: could not match 'shared_ptr<type-parameter-0-2>' against 'char const[3]'
operator<<(basic_ostream<_CharT, _Traits>& __os, shared_ptr<_Yp> const& __p);
^
/usr/include/c++/v1/string_view:813:1: note: candidate template ignored: could not match 'basic_string_view<type-parameter-0-0, type-parameter-0-1>' against 'const char *'
operator<<(basic_ostream<_CharT, _Traits>& __os,
^
/usr/include/c++/v1/string:4425:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'char const[3]'
operator<<(basic_ostream<_CharT, _Traits>& __os,
^
/usr/include/c++/v1/regex:5320:1: note: candidate template ignored: could not match 'sub_match<type-parameter-0-2>' against 'char const[3]'
operator<<(basic_ostream<_CharT, _ST>& __os, const sub_match<_BiIter>& __m)
^
EquationTags.cc:75:40: error: use of undeclared identifier 'endl'; did you mean 'end'?
             << key << " " << value << endl;
                                       ^~~~
                                       end
/usr/include/c++/v1/initializer_list:108:1: note: 'end' declared here
end(initializer_list<_Ep> __il) _NOEXCEPT
^
EquationTags.cc:81:10: error: invalid operands to binary expression ('std::ostream' (aka 'basic_ostream<char>') and 'const char [22]')
  output << "M_.equations_tags = {" << endl;
  ~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~

Dynare-5.0

clang-12

FreeBSD 13