...so that only a single one ends up in the .xcd data.  (In the given case,
introduced with 838b77f5 "Resolves: rhbz#1065807
use xdg ~/Templates for default Template location," the duplication for the
unixdesktop case happened to be harmless, as the non-unixdesktop <value>
appeared in a block in main.xcd before the unixdesktop-specific <value>, so the
former was effectively ignored when reading main.xcd.)

Change-Id: I5199556ee3e6decaa07beb14a0503e1b5661f5df