package/wlroots: always disable xcb-errors

Stop trying to enable the xcb-errors Meson option and always disable it:
there is no xcb-util-errors package in Buildroot. The build recipe was
wrongly assuming that the XCB errors library would be installed as part
of the xcb-util package, which is not the case.

Fixes the following autobuilder failure:

  http://autobuild.buildroot.net/results/1891aa624b29e4bbcbbe6bc752a1cc90c316024e/



Signed-off-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>