binarycreator fails to create archive if temporary directory contains spaces

The binarycreator program fails to generate a 7zip archive if the temporary directory contains spaces. This is not uncommon on Windows since the temporary directory is in e.g. C:\Users\<username\AppData\Local\Temp. If the user name contains spaces (e.g. "Frerich Raabe"), binarycreator faills. Setting the TMP environment variable to a path which does not contain spaces works around the issue.

The reason for this is that the createArchive function in src/libs/installer/lib7z_facade.cpp assembles a command line via

        const UString command = QString2UString(
            // (mode: add) (type: 7z) (time: modified|creation|access) (threads: multi-threaded)
            QLatin1String("a -t7z -mtm=on -mtc=on -mta=on -mmt=on ")
#ifdef Q_OS_WIN
            + QLatin1String("-sccUTF-8 ") // (files: case-sensitive|UTF8)
#endif
            + QString::fromLatin1("-mx=%1 ").arg(int(level)) // (compression: level)
            + QDir::toNativeSeparators(target) + QLatin1Char(' ')
            + QDir::toNativeSeparators(sources.join(QLatin1Char(' ')))
        );

...but neglects escaping the 'target' argument or any of the 'sources' values.