src/tools/bootstrap was already compiled with QT_USE_STRINGBUILDER,
by way of load(qt_module), but the actual apps weren't.

Some apps become smaller, some larger; all (presumably) faster.

Change-Id: Idc8662e62ec14b27e730de9842bec295a1b5566e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>