Fix broken Linux install

In commit ca8aee4701f9 ("Move the XSLT files into a Qt resource") we
removed a line from the .pri file without removing the trailing '\' from
the previous line which caused the following line to be consumed by the
assignment - and the dummy target not being added to the EXTRA_TARGETS...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>