Translations:Compile on Linux/271/en

By default, FreeCAD 0.19 and earlier build for Python 2 and Qt4. Since these two packages are obsolete, it is better to build for Python 3 and Qt5. Support for Python 2 and Qt4 has been removed in FreeCAD 0.20 and it is not necessary to explicitly enable Qt5 and Python 3 if compiling the latest development versions.