tinderbox <-> gerrit-buildbot integration: passing build specific configuration options

As Markus pointed out in comment on that change[1] it is useless and
annoying to schedule a build on something that is not get verified
during the build, because the configuration options aren't activated.

I wonder how hard would it be to accept configure options during build
scheduling? With new upcoming major Gerrit release 2.8 the Plugin API
was extended, so we could add a Schedule button and even a popup dialog
and gather additional user input, like optional platforms to build and
optional configuration option to activate during the build. In example
above, the following option could be passed:

--enable-extension-integration
--enable-ext-wiki-publisher

(Assuming that Java is installed and --with-java is activated on all
tb).

Check screen shots from the WIP plugin to see a button placed from a
plugin with optional popup dialog [2].

[1] https://gerrit.libreoffice.org/6454
[2] https://github.com/davido/gerrit-wip-plugin

--David