xbase: mark `broken` for removal

Fails to build on `gcc-14` as https://hydra.nixos.org/build/300549105:

xbstring.cpp: In member function 'xbString& xbString::sprintf(const char*, ...)':
xbstring.cpp:297:3: error: 'va_start' was not declared in this scope
297 | va_start(ap, format);
| ^~~~~~~~
xbstring.cpp:314:3: error: 'va_end' was not declared in this scope
314 | va_end(ap);
| ^~~~~~

pkgs/by-name/xb/xbase/package.nix

···
     homepage = "https://sourceforge.net/projects/xdb/";
     description = "C++ class library formerly known as XDB";
     platforms = platforms.linux;
+    broken = true; # Fails to build against gcc-14, no upstream activity.
     license = licenses.lgpl2;
   };
 }