[Development] Proposal: move Qt provisioning scripts and 3rd party components into a dedicated repo

[Alexandru Croitor]

Hi,

Just pointing to some relevant issues and discussions.

https://bugreports.qt.io/browse/QTBUG-68816
https://bugreports.qt.io/browse/QTBUG-73760
https://wiki.qt.io/QtCS2018_Third-Party_Sources_Policy_and_Security

> For us as Qt developers it might mean that we either have to build that 3rd party repository ourselves (which could still be done as part of the toplevel build process)

If the libraries will be built using their native build system instead of CMake, that will complicate the implementation of top-level builds, as well considerably slow down configuration time, because the 3rd party libs will need to be built and installed in some staging area before CMake can pick them up for Qt usage at configure time.
So qt5/configure would imply first running configure && make && make install for each 3rd party library.