/usr/share/qt4/mkspecs/features/unix/ is in qt4-qmake 4:4.8.1-0ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/share/qt4/mkspecs/features/unix/bsymbolic_functions.prf
/usr/share/qt4/mkspecs/features/unix/dylib.prf
/usr/share/qt4/mkspecs/features/unix/gdb_dwarf_index.prf
/usr/share/qt4/mkspecs/features/unix/hide_symbols.prf
/usr/share/qt4/mkspecs/features/unix/largefile.prf
/usr/share/qt4/mkspecs/features/unix/opengl.prf
/usr/share/qt4/mkspecs/features/unix/openvg.prf
/usr/share/qt4/mkspecs/features/unix/separate_debug_info.prf
/usr/share/qt4/mkspecs/features/unix/thread.prf
/usr/share/qt4/mkspecs/features/unix/x11.prf
/usr/share/qt4/mkspecs/features/unix/x11inc.prf
/usr/share/qt4/mkspecs/features/unix/x11lib.prf
/usr/share/qt4/mkspecs/features/unix/x11sm.prf