wagyu seems to break image building

[robe]

I'm not sure why, but I think enabling wagyu broke debbie image building and pdf building.

Just noticed it when I had no pdf generated for the alpha2 release.

to confirm that was the issue, I changed her dist scripts to --without-wagyu at r17460

and she seems to be building now.

When wagyu was enabled, got this error: ​https://debbie.postgis.net/job/PostGIS_Make_Dist/label=debbie/1034/console

23:06:23 lwin_geojson.c:36:10: fatal error: json.h: No such file or directory
23:06:23  #include <json.h>
23:06:23           ^~~~~~~~
23:06:23 compilation terminated.
23:06:23 make[2]: *** [Makefile:199: lwin_geojson.lo] Error 1
23:06:23 make[2]: Leaving directory '/var/lib/jenkins/workspace/PostGIS_Make_Dist/label/debbie/6a1a4284093100b6282298ba4cdd32799d9e68a0/liblwgeom'
23:06:23 make[1]: *** [Makefile:196: ../../../liblwgeom/.libs/liblwgeom.a] Error 2
23:06:23 make[1]: Leaving directory '/var/lib/jenkins/workspace/PostGIS_Make_Dist/label/debbie/6a1a4284093100b6282298ba4cdd32799d9e68a0/doc/html/image_src'
23:06:23 make: *** [Makefile:341: images] Error 2
23:06:23 /usr/bin/xsltproc --novalid ./xsl/postgis_aggs_mm.xml.xsl postgis-out.xml > postgis_aggs_mm.xml
23:06:24 if test x"dbtoepub" = x; then \
23:06:24    echo "Error: dbtoepub not found, can't build epub"; \
23:06:24    echo "       try installing dbtoepub"; \
23:06:24    false; \
23:06:24 else \
23:06:24 	dbtoepub -c "/var/lib/jenkins/workspace/PostGIS_Make_Dist/label/debbie/6a1a4284093100b6282298ba4cdd32799d9e68a0/doc/html/style.css" \
23:06:24 	 -o postgis-3.0.0alpha2.epub \
23:06:24 	  postgis-out.xml; \
23:06:24 fi
23:07:49 /usr/lib/ruby/2.5.0/fileutils.rb:1291:in `initialize': No such file or directory @ rb_sysopen - /var/lib/jenkins/workspace/PostGIS_Make_Dist/label/debbie/6a1a4284093100b6282298ba4cdd32799d9e68a0/doc/images/st_issimple01.png (Errno::ENOENT)
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:1291:in `open'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:1291:in `copy_file'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:432:in `copy_file'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:359:in `block in cp'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:1463:in `block in fu_each_src_dest'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:1479:in `fu_each_src_dest0'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:1461:in `fu_each_src_dest'
23:07:49 	from /usr/lib/ruby/2.5.0/fileutils.rb:358:in `cp'
23:07:49 	from /usr/lib/ruby/vendor_ruby/dbtoepub/docbook.rb:190:in `block in copy_images'
23:07:49 	from /usr/lib/ruby/vendor_ruby/dbtoepub/docbook.rb:180:in `each'
23:07:49 	from /usr/lib/ruby/vendor_ruby/dbtoepub/docbook.rb:180:in `copy_images'
23:07:49 	from /usr/lib/ruby/vendor_ruby/dbtoepub/docbook.rb:112:in `bundle_epub'
23:07:49 	from /usr/lib/ruby/vendor_ruby/dbtoepub/docbook.rb:54:in `render_to_file'
23:07:49 	from /usr/bin/dbtoepub:72:in `block in <main>'

What's annoying is the run shows success, so it's not triggering a fail when it should be. That another issue.

The make document scripts haven't been touched for a while, so maybe they are using old syntax for enabling json.

[Algunenano]

This was fixed in #4443; wagyu was dropping CPPFLAGS in some cases.