This adds a -skip-googlemaps option to the build script since for some
reason trying to build the googlemaps plugin in the Travis mac
environment causes an error with a missing stack-protector-strong
feature.
The build relies on a custom build Qt and a cached homebrew environment.
And the result is of course not a DMG with a signed app but a zip file
with an unsigned app - so it's a bit harder to consume.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
