I filed the linked bug and am the technical owner of Firefox's build system.
There were efforts made and discussions outside of the linked bug. To say "nothing" was done is just not true.
It would be more accurate to say that we just can't justify working on this right now because the timing isn't right and it's high cost for perceived low reward. The time of everyone involved to implement this would be better spent on improvements that benefit the general Firefox population. Some of those improvements include overhauling Firefox's build automation to better support things like building with Docker. That lays the groundwork for (easier) deterministic builds in the future. Even then, I'm not sure if this will happen. Brendan's post called on the larger community to make requests of Mozilla. That front has been surprisingly quiet. If you really want this, I would suggest making noise on the mozilla.org domain. Even better, contribute some patches, like the Tor Project has done: I will happily review them! #build on irc.mozilla.org.
Sorry if I wrote that nothing was done. What I really meant was that no change happened, and even the discussion for the bug at a first glance doesn't let understand if there is a clear path toward deterministic builds.
What would it be "making noise on the mozilla.org domain"?
Must say, though, I am kind of saddened to see that this discussion was upvoted 80 times while the bug is still at 6.
The path towards deterministic builds is definitely not clear. As many in this thread have pointed out, it's a difficult technical problem. The difficulties are multiplied by a project at Firefox's scale.
Further complicating matters is our platform breakdown. The majority of Firefox users are on Windows. Deterministic builds on Windows are very painful. And that's before you figure PGO into the mix. Tor works around this by compiling Firefox with an open source toolchain and doesn't use PGO. But that's a non-starter for us because choosing an open source toolchain over Microsoft's would result in performance degradations for our users. Believe me, if we could ship a Windows and Mac Firefox built with 100% open source to no detriment to our users, we would. There's work to get Firefox building with Clang on Windows (but only for doing ASAN and static analysis, not for shipping to users). That gets us one step closer.
All that being said, there has been exploratory talk lately of serving segments of our user base with specialized Firefox builds. e.g. a build with developer tools front and center that caters to the web development community. If that ever happens, I imagine a deterministically-built Firefox with things like Tor built in could be on the table. The way you can make that happen is to direct noise directly at the Mozilla community. Send a well-crafted email to firefox-dev (https://mail.mozilla.org/listinfo/firefox-dev) explaining your position. Anticipate that people will likely reply by asking you to prioritize this against existing goals, such as shipping 64-bit Firefox on Windows and shipping multi-process Firefox. We don't have nearly unlimited resources like some of the other browser vendors, so we can't just do everything. Again, I implore people to directly contribute to Mozilla any way they can. https://www.mozilla.org/contribute/
I went to the Debian talk on reproducible builds at Fosdem this year which was interesting, but there is still a fair amount of work to do to make this more routine, but the pieces are being worked on and this will get easier as it becomes more normal.
There were efforts made and discussions outside of the linked bug. To say "nothing" was done is just not true.
It would be more accurate to say that we just can't justify working on this right now because the timing isn't right and it's high cost for perceived low reward. The time of everyone involved to implement this would be better spent on improvements that benefit the general Firefox population. Some of those improvements include overhauling Firefox's build automation to better support things like building with Docker. That lays the groundwork for (easier) deterministic builds in the future. Even then, I'm not sure if this will happen. Brendan's post called on the larger community to make requests of Mozilla. That front has been surprisingly quiet. If you really want this, I would suggest making noise on the mozilla.org domain. Even better, contribute some patches, like the Tor Project has done: I will happily review them! #build on irc.mozilla.org.