New tests coming to opt builds and l10n repacks

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 600838 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.

As of now, these tests are running on Linux (32 and 64 bit) and Windows opt en-US builds only, across all branches (including Try). Sometime next week these tests will be turned on for the remaining opt builds and l10n repacks, except the Mac ones on 1.9.1 and 1.9.2, which fail for unknown reasons, and aren't worth debugging due to their limited life going forward.