x11-wm/mutter: unbreak with libglvnd

In file included from ../cogl/cogl/driver/nop/cogl-clip-stack-nop.c:34:
In file included from ../cogl/cogl/driver/nop/cogl-clip-stack-nop-private.h:38:
In file included from ../cogl/cogl/cogl-context-private.h:44:
In file included from ../cogl/cogl/cogl-driver.h:36:
In file included from ../cogl/cogl/cogl-framebuffer-private.h:37:
In file included from ../cogl/cogl/cogl-journal-private.h:37:
In file included from ../cogl/cogl/cogl-fence-private.h:36:
In file included from ../cogl/cogl/winsys/cogl-winsys-private.h:38:
In file included from ../cogl/cogl/winsys/cogl-texture-pixmap-x11-private.h:45:
In file included from ../cogl/cogl/cogl-texture-private.h:40:
In file included from ../cogl/cogl/cogl-texture-2d.h:44:
cogl/cogl/cogl-egl-defines.h:38:10: fatal error: 'EGL/eglmesaext.h' file not found
#include <EGL/eglmesaext.h>

^~~~~~~~~~~~~~~~~~