New tests coming to Linux and Windows opt builds

For a couple of years now we've been building Firefox release builds using slightly different packaging targets than nightly builds. This has streamlined our release automation in some ways, but has had the unfortunate side effect of release build packaging targets being largely untested. This week, we will start correcting that. When bug 600832 lands we will start testing the release build packaging code ("MOZ_PKG_PRETTYNAMES"). These packages will not be uploaded anywhere, but any build that fails in one of these targets will constitute a test failure, and turn the overall build orange. By doing so, we can ensure that any bustages to them will be caught at commit time, rather than during a release.

For now, these tests will be run on all Linux (32 and 64 bit) and Windows en-US opt builds, including nightlies, but will make their way to Mac builds and l10n repacks shortly.