main/libxkbcommon: depend on xkeyboard-config
According to the README of libxkbcommon:
libxkbcommon does not distribute a keymap dataset itself, other than for testing purposes. The most common dataset is xkeyboard-config, which is used by all current distributions for their X11 XKB data. More information on xkeyboard-config is available here: https://www.freedesktop.org/wiki/Software/XKeyboardConfig
The dataset for Compose is distributed in libX11, as part of the X locale data.
fixes #11586 (closed)