xwayland/glamor/gbm: use GBM_FORMAT_ARGB8888 for 24-bit depth on GL ES
On some drivers (mesa included), when we request GBM_FORMAT_XRGB8888, driver set surface storage format to GL_RGB8, which breaks gles2 rendering. If we force set gbm_format to GBM_FORMAT_ARGB8888, then rendering will happen and working.
This is a screenshot of XWayland VirtualBox with !934 (merged) and MESA_GL_VERSION_OVERRIDE=2.0
Without !934 (merged), I will get black window instead of VirtualBox (#1356 (closed)).
Fixes #1288 (closed) Fixes #1356 (closed)
Request for review: @ofourdan @ajax @anholt
Fixes: mesa/mesa!5034 (merged)
Edited by Konstantin