tools: use QStringBuilder

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>

mkspecs/features/qt_tool.prf

@@ -12,6 +12,7 @@
 load(qt_app)
 
 CONFIG += console
+DEFINES *= QT_USE_QSTRINGBUILDER
 
 # If we are doing a prefix build, create a "module" pri which enables
 # qtPrepareTool() to work with the non-installed build.

src/tools/bootstrap/bootstrap.pro

@@ -103,6 +103,7 @@ SOURCES += \
            ../../corelib/tools/qsize.cpp \
            ../../corelib/tools/qline.cpp \
            ../../corelib/tools/qstring.cpp \
+           ../../corelib/tools/qstringbuilder.cpp \
            ../../corelib/tools/qstring_compat.cpp \
            ../../corelib/tools/qstringlist.cpp \
            ../../corelib/tools/qvector.cpp \