devel/llvm14: fix build with clang 19

Clang 19 now implements CWG 96 [1], which requires a template argument
list after a 'template' keyword, resulting in errors similar to:

   
/wrkdirs/usr/ports/devel/llvm14/work/llvm-project-14.0.6.src/flang/include/flang/Evaluate/integer.h:310:32:
error: a template argument list is expected after a name prefixed by the
template keyword [-Wmissing-template-arg-list-after-template-kw]
      310 |       auto back{FROM::template ConvertSigned(result.value)};
          |                                ^
   
/wrkdirs/usr/ports/devel/llvm14/work/llvm-project-14.0.6.src/flang/lib/Evaluate/fold-real.cpp:72:22:
warning: variable 'z' set but not used [-Wunused-but-set-variable]
       72 |     } else if (auto *z{UnwrapExpr<Expr<SomeComplex>>(args[0])}) {
          |                      ^
   
/wrkdirs/usr/ports/devel/llvm14/work/llvm-project-14.0.6.src/flang/lib/Evaluate/fold-real.cpp:69:15:
warning: variable 'x' set but not used [-Wunused-but-set-variable]
       69 |     if (auto *x{UnwrapExpr<Expr<SomeReal>>(args[0])}) {
          |               ^
   
/wrkdirs/usr/ports/devel/llvm14/work/llvm-project-14.0.6.src/flang/lib/Evaluate/fold-real.cpp:148:60:
error: a template argument list is expected after a name prefixed by the
template keyword [-Wmissing-template-arg-list-after-template-kw]

devel/llvm14: fix build with libc++ 19

As noted in the libc++ 19 release notes [1], std::char_traits<> is now
only provided for char, char8_t, char16_t, char32_t and wchar_t, and any
instantiation for other types will fail.

This causes devel/llvm14 to fail to compile with clang 19 and libc++
19, resulting in errors similar to:

    /usr/include/c++/v1/string:820:42: error: implicit instantiation of
undefined template 'std::char_traits<unsigned char>'
      820 |   static_assert(is_same<_CharT, typename
traits_type::char_type>::value,
          |                                          ^
   
/wrkdirs/usr/ports/devel/llvm14/work-default/llvm-project-14.0.6.src/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp:603:34:
note: in instantiation of template class 'std::basic_string<unsigned char>'
requested here
      638 |       std::basic_string<uint8_t> zeros(reg_info.byte_size, '\0');
          |                                  ^