Don't call setlocale(3) in bootstrap code

When bootstrapping we might rely on sscanf(3) for parsing doubles from
strings. We don't want this to be localized.

Task-number: QTBUG-49616
Change-Id: I1607bb750b479fd7007dd0d875d600be59caa859
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/corelib/kernel/qcoreapplication.cpp

@@ -565,7 +565,7 @@ void QCoreApplicationPrivate::initLocale()
     if (qt_locale_initialized)
         return;
     qt_locale_initialized = true;
-#ifdef Q_OS_UNIX
+#if defined(Q_OS_UNIX) && !defined(QT_BOOTSTRAPPED)
     setlocale(LC_ALL, "");
 #endif
 }