"Build debugging helpers" seems to fail when only qmldump could not be built

Maemo users currently have to build the C++ debugging helpers, because the gdb there has no Python support. When they click on "Rebuild" in the Qt versions dialog, they get what seems to be an error indication, because qmldump could not be built. However, that tool is not relevant to pure C++ debugging, and that should be made more clear. Also, the entry third column of the Qt version changes to a horizontal red line, whose meaning is unclear.