build problems with man pages on linux

[Philip Race]

I've been working on Windows and Mac issues for the last several weeks 
so it has
been some time since I even tried to build JDK on my Ubuntu 1604 system.
In the interim it seems to have stopped working. I get these errors :

LauncherCommon.gmk:223: recipe for target 
'/build/linux-x86_64-server-release/support/markdown/BUILD_MAN_PAGES_keytool.md_post.tmp' 
failed
Creating support/modules_cmds/java.rmi/rmid from 1 file(s)
Creating support/modules_cmds/java.rmi/rmiregistry from 1 file(s)
LauncherCommon.gmk:223: recipe for target 
'/build/linux-x86_64-server-release/support/markdown/BUILD_MAN_PAGES_rmid.md_post.tmp' 
failed
make/Main.gmk:228: recipe for target 'java.rmi-launchers' failed
LauncherCommon.gmk:223: recipe for target 
'/build/linux-x86_64-server-release/support/markdown/BUILD_MAN_PAGES_java.md_post.tmp' 
failed
make/Main.gmk:228: recipe for target 'java.base-launchers' failed

Could it be related to this fix
changeset:   59638:88ba70c9da28
user:        ihse
date:        Sat Jun 06 02:04:21 2020 +0200
summary:     8246435: Replace Javascript implementation of pandoc 
filters with Java


In case it is relevant configure always reports ...

checking for pandoc... /usr/bin/pandoc
checking if the pandoc smart extension needs to be disabled for 
markdown... pandoc: unrecognized option `--list-extensions'
Try pandoc --help for more information.

.. but it is not clear .. that has never been a problem before.

-phil