Cannot build qbs with mingw-builds with message "QString::QString(const char *) is private"

When building qbs bundled in Qt Creator 3.4.1 with mingw-builds(both 4.9.2rev3 and 5.1.0 rev0), I encountered the error "QString::QString(const char *) is private" on line 108 of file src/lib/corelib/tools/filetime_win.cpp. It seems to be related to QString header file when QT_NO_CAST_FROM_ASCII is defined, but I have no idea on details.

You can see the line looks like this:

const QString result = QString("%1.%2.%3 %4:%5:%6")

I changed the line like this, but it's just workaround and not fundamental resolution:

const QString result = QString(QLatin1String("%1.%2.%3 %4:%5:%6"))

I know QString::QString(const char *) cannot be private, as Qt Documentation says, and on my sample application it works, but this error occurs only on building qbs. Any ideas or fundamental resolutions?