As demonstrated by commit b875362c,
scp2 will reference all languages' UIConfig zip file, but gbuild only
builds those that have existing input files from translations;
tweak UIConfig class to always build a zip file, and the Zip command to
work with no inputs as well, which requires a little hack.

Change-Id: If6dbb07aa856c94802b9abdcaa20ba03e59d37fa