lang/basic256 runtime error

[Fernando Apesteguía]

Hi there!

I was testing some changes to lang/basic256 from PR 235204 and I
realized the port is broken at run time with this error:

ld-elf.so.1: /usr/local/lib/qt5/libQt5SerialPort.so.5: Undefined
symbol "_ZN16QIODevicePrivate13putCharHelperEc at Qt_5_PRIVATE_API"

I don't know exactly when or why this ibroke. Is comms/qt5-serialport
working fine?

tijl@ in copy since it seems he did some fixes (r490472) related to
Qt_5_PRIVATE_API so he might know what this is about.

Thanks in advance!