wxWidgets 3.1.5+ on Linux will compile with the Wayland EGL
canvas as the backend instead of the X11 backend. This requires a
version of GLEW compiled with the proper EGL defines and a different
header/code for certain parts that are X11 GLEW specific.
This introduces an in-tree version of GLEW that will be built with the
GLEW_EGL flag then statically linked into the KiCad executables when
EGL support is needed.