SetupShibokenAndPyside macro checks module include path and eventually
decides to disable respective module in case its include directory is
missing. Make this process more straightforward by testing directory
existence; "Location: " string is 10 not 9 characters long and leading
whitespace makes testing for directory name fail.
While there, rename variables to respect that find_pip_package returns
only single include and library path.
* fix syntax error with message()
* if shiboken/PySide cannot be found print a warning instead of fatal error. Especially for Qt6 builds a self-compiled shiboken6/PySide6 is required that isn't necessarily installed into the system directories so that the (system) Python interpreter may fail to find them
Removes the BUILD_QT5 flag and adds a new FREECAD_QT_VERSION option,
which can be set to either "Auto" (default), 5, or 6. Auto detects which
version of Qt is installed on the system and chooses it. If both version
are installed, Qt5 is used.
Note that this DOES NOT implement compiling against Qt6, it only adds
the necessary cMake infrastructure to begin work on the source code
changes that will be required.
