webkitgtk-2.24.1 fails with KHR/khrplatform.h missing

[ng0%n0.is@localhost]

I'm not sure if I have an outdated dependency somewhere, but since last night webkitgtk-2.24.1 fails
on a new (~26 hours ago) build of -CURRENT.

Scanning dependencies of target WebCore
[ 53%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/html/canvas/ANGLEInstancedArrays.cpp.o
In file included from /usr/X11R7/include/GL/gl.h:2055:0,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/platform/graphics/OpenGLShims.h:23,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/platform/graphics/ANGLEWebKitBridge.h:56,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/platform/graphics/GraphicsContext3D.h:28,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/html/canvas/WebGLRenderingContextBase.h:33,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/html/canvas/WebGLExtension.h:28,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/html/canvas/ANGLEInstancedArrays.h:28,
                 from /usr/work/www/webkit-gtk/work/webkitgtk-2.24.1/Source/WebCore/html/canvas/ANGLEInstancedArrays.cpp:29:
/usr/X11R7/include/GL/glext.h:467:10: fatal error: KHR/khrplatform.h: No such file or directory
 #include <KHR/khrplatform.h>
          ^~~~~~~~~~~~~~~~~~~
compilation terminated.
gmake[2]: *** [Source/WebCore/CMakeFiles/WebCore.dir/build.make:787: Source/WebCore/CMakeFiles/WebCore.dir/html/canvas/ANGLEInstancedArrays.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:929: Source/WebCore/CMakeFiles/WebCore.dir/all] Error 2
gmake: *** [Makefile:152: all] Error 2
*** Error code 2

Stop.
make[2]: stopped in /usr/pkgsrc/www/webkit-gtk
*** Error code 1

Stop.
make[1]: stopped in /usr/pkgsrc/www/webkit-gtk
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/finance/gnucash