xwayland/glx: Enable sRGB fbconfigs

We turn this on if the GL underneath us can enable GL_FRAMEBUFFER_SRGB.
We do try to generate both capable and incapable configs, which is to
keep llvmpipe working until the client side gets smarter about its srgb
capabilities.
5 jobs for glx-egl-srgb-fbconfigs in 6 minutes and 55 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Docker Image
passed debian-buster #11718737

00:00:24

 
  Build And Test
passed autotools #11718738

00:06:30

passed meson #11718739

00:02:38

passed meson-noglamor #11718740

00:01:30

passed mingw-cross-build #11718741

00:00:43