wgpu-hal: Work around cbindgen bug: ignore gles::egl module.

The definition of `EglInstance` trips mozilla/cbindgen#286. Since
the `wgpu_hal::gles::egl` module is an implementation detail anyway,
it should be harmless to ask cbindgen to just ignore it.

Fixes gfx-rs#2575.

wgpu-hal/src/gles/mod.rs

@@ -56,6 +56,7 @@ To address this, we invalidate the vertex buffers based on:
 
 */
 
+///cbindgen:ignore
 #[cfg(any(not(target_arch = "wasm32"), feature = "emscripten"))]
 mod egl;
 #[cfg(all(target_arch = "wasm32", not(feature = "emscripten")))]