Bug 40742: Add Privacy Browser targets

Merge Info

Related Issues

• #40742 (closed)
• #40745 (closed)
• #40753 (closed)

Backport Timeline

• Immediate - patchsets for critical bug fixes or other major blocker (e.g. fixes for a 0-day exploit) OR patchsets with trivial changes which do not need testing (e.g. fixes for typos or fixes easily verified in a local developer build)
• Next Minor Stable Release - patchset that needs to be verified in nightly before backport
• Eventually - patchset that needs to be verified in alpha before backport
• No Backport - patchset for the next major stable

Issue Tracking

• Link resolved issues with appropriate Release Prep issue for changelog generation

Change Description

This MR should allow us to build Privacy Browser build.

It introduces the following changes:

1. it allows us to customize MOZ_APP_BASENAME, which has direct effects on the output paths and filenames
2. it adds a few needed files for the Windows and macOS installers
3. it adds the privacybrowser targets
4. it adds the torbrowser- prefix to the Makefile targets for generating updates
5. it adds privacybrowser to the .gitignore (and adds back release, alpha and nightly to guarantee compatibility with older builds and with maint-12.0)
6. it updates the needed documentation

So far, the builds work, but only if you use the single target. Group targets (such as desktop) don't work, but I cannot fix them on my own.