angle is an implementation of es2 and thus autodetected if es2 is
requested.
but this also means that it is actually *not* mutually exclusive
with dynamicgl - quite the opposite. express that sensibly in the
build system. this implies that we will now get sensible messages
from configure if angle is not detected while building with dynamicgl.
furthermore, this simplifies the handling of defaults, removes the
unnecessary case in checkAvailability() (checkAngleAvailability() is
always called directly), fixes the complaint on winrt if gles2 is
disabled, and avoids redundant checks for the purpose of obtaining
an error message.
Change-Id: I3373f0ad7d5484d1bac8dbde3f8ee6fca89ebcb8
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
0492f4a4c5