qilinguist: generate more stable .po{,t} files
qilinguist: generate more stable .po{,t} files

invoke xgettext with option to avoid timestamps
in order to make its output more stable in time
(ie. less subject to irrelevant changes).

Because .po and .pot are usually under version control,
those irrelevant changes are an annoyance to the developer:
calling "qilinguist update" leads to the git repository
being skipped by qisrc because of "unstaged changes".

Change-Id: I2bb3621e3099d27e2c077ee1c1a038005a662aaf

aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild