wayland wont build anymore due to missing docbook xml/xsl

[wwwutz]

PR #1581 killed wayland build.

make[3]: Entering directory '/scratch/local2/beehive/wayland-1.16.0-0/buildroot/wayland/wayland-1.16.0-0/build/doc/publican'
/usr/bin/xmlto --skip-validation --stringparam chunk.section.depth=0 --stringparam toc.section.depth=1 --stringparam html.stylesheet=css/default.css html ./en-US/Wayland.xml -o ./Wayland/en-US/html
I/O error : Attempt to load network entity http://docbook.sourceforge.net/release/xsl/current/html/chunk.xsl
warning: failed to load external entity "http://docbook.sourceforge.net/release/xsl/current/html/chunk.xsl"
compilation error: file /scratch/local/xmlto-xsl.JsXrra line 4 element import
xsl:import : unable to load http://docbook.sourceforge.net/release/xsl/current/html/chunk.xsl
make[3]: *** [Makefile:558: Wayland] Error 5
make[3]: Leaving directory '/scratch/local2/beehive/wayland-1.16.0-0/buildroot/wayland/wayland-1.16.0-0/build/doc/publican'
make[2]: *** [Makefile:375: all-recursive] Error 1
make[1]: *** [Makefile:1976: all-recursive] Error 1
make: *** [Makefile:1187: all] Error 2

[wwwutz]

fixed by #1598