gnucash-docs maint: Apply source/dest figure dependencies to AddXdgHelpTarget.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash-docs/commit/a8c855a8 (commit)
	from  https://github.com/Gnucash/gnucash-docs/commit/e803940d (commit)



commit a8c855a80ea119c003cafd1e6a9e1db262694aec
Author: John Ralls <jralls at ceridwen.us>
Date:   Thu Sep 8 16:21:14 2022 -0700

    Apply source/dest figure dependencies to AddXdgHelpTarget.



Summary of changes:
 cmake/AddXdgHelpTarget.cmake | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)