KICAD_USE_EGL: flag should not be necessary

Building kicad with Debian Unstable:

In file included from /build/kicad/src/kicad/include/gal/opengl/vertex_common.h:35,
                 from /build/kicad/src/kicad/include/gal/opengl/vertex_item.h:35,
                 from /build/kicad/src/kicad/common/gal/opengl/vertex_item.cpp:32:
/build/kicad/src/kicad/include/gal/opengl/kiglew.h:53:14: error: #error "KICAD_USE_EGL must be defined since wxWidgets has been compiled with the EGL canvas"

Umm … why don't you autodetect this? should be reasonably trivial.

KiCad Version

current master