cairo: make OpenGL support require X11

If OpenGL is enabled without X11, the build fails with:

In file included from /nix/store/<...>-libglvnd-1.3.1-dev/include/EGL/egl.h:39,
                 from cairo-gl.h:130,
                 from cairo-gl-private.h:51,
                 from cairo-gl-composite.c:48:
/nix/store/<...>-libglvnd-1.3.1-dev/include/EGL/eglplatform.h:128:10: fatal error: X11/Xlib.h: No such file or directory
  128 | #include <X11/Xlib.h>
      |          ^~~~~~~~~~~~
compilation terminated.

1 files changed, 2 insertions, 2 deletions

diff --git a/pkgs/development/libraries/cairo/default.nix b/pkgs/development/libraries/cairo/default.nix
index 628046a5741..a414191ac0d 100644
--- a/pkgs/development/libraries/cairo/default.nix
+++ b/pkgs/development/libraries/cairo/default.nix
@@ -4,13 +4,13 @@
 , gobjectSupport ? true, glib
 , xcbSupport ? x11Support, libxcb, xcbutil # no longer experimental since 1.12
 , libGLSupported ? stdenv.lib.elem stdenv.hostPlatform.system stdenv.lib.platforms.mesaPlatforms
-, glSupport ? config.cairo.gl or (libGLSupported && stdenv.isLinux)
+, glSupport ? x11Support && config.cairo.gl or (libGLSupported && stdenv.isLinux)
 , libGL ? null # libGLU libGL is no longer a big dependency
 , pdfSupport ? true
 , darwin
 }:
 
-assert glSupport -> libGL != null;
+assert glSupport -> x11Support && libGL != null;
 
 let
   version = "1.16.0";