build failure on ubuntu 18.04

Hi all,

I'm a newbie on the libreoffice front, and I'm tracking down a bug that I've discovered in writer. Rather than posting a symptom-only bug, I've been trying to build a debug version of libreoffice 7.0.0, but the build keeps failing with the message as follows:

<-snip->

[CXX] sal/rtl/math.cxx
[CXX] workdir/UnpackedTarball/skia/tools/sk_app/unix/VulkanWindowContext_unix.cpp
[CXX] workdir/UnpackedTarball/skia/third_party/skcms/skcms.cpp
/home/ron/libreoffice/workdir/UnpackedTarball/skia/tools/sk_app/unix/VulkanWindowContext_unix.cpp:19:10: fatal error: X11/Xlib-xcb.h: No such file or directory
#include <X11/Xlib-xcb.h>
^~~~~~~~~~~~~~~~
compilation terminated.
/home/ron/libreoffice/solenv/gbuild/LinkTarget.mk:347: recipe for target '/home/ron/libreoffice/workdir/GenCxxObject/UnpackedTarball/skia/tools/sk_app/unix/VulkanWindowContext_unix.o' failed
make[1]: *** [/home/ron/libreoffice/workdir/GenCxxObject/UnpackedTarball/skia/tools/sk_app/unix/VulkanWindowContext_unix.o] Error 1
make[1]: *** Waiting for unfinished jobs....
Makefile:282: recipe for target 'build' failed
make: *** [build] Error 2

My autogen.sh command looks like this:

./autogen.sh --enable-debug --x-includes=/snap/gnome-3-34-1804/36/usr/include/

The file Xlib-xcb.h exists in the directory in the X11 directory which in turn is a child of the one listed in the --x-includes path indicated above. The file permission is 0644 for the .h file, owner is root.

Can anyone give me some guidance on how to proceed?

Thanks in advance.

Ron