Fixes case-insensitive file systems confusing gst-libs/gst/gl/egl/egl.h with EGL/egl.h when the source directory gst-libs/gst/gl is automatically added to the compiler's search path.
Due to https://github.com/mesonbuild/meson/issues/7582 we also need to perform manual enumtype generation.
Fixes #814 (closed)