Tor Browser dev build cannot launch tor

This happens to me on Linux Mint 21 (which I beleive is based on the 22.04 Ubunutu series). I did an in-place upgrade from Linux Mint 20.3 before this behaviour started happening. I have not tested to see if this happens on a fresh Linux install.

From IRC:

<richard> ok mystery.. not solved but narrowed down
<richard> so for some context, i'm having this tor failed to launch issue on my desktop PC which i just upgraded to Linux Mint 21 (based off of the latest ubuntu)
<richard> (this PC used to be able to build/run tor-browesr in the past no probem)
<richard> so, the issue occurs 
<richard> when build tor-browseer and deploy over a freshly fetch'd 12.0a4 bundle
<richard> launch tor-browser, and it tries to launch tor, and tor exits with 127 error code (haven't tracked down deeper than that)
<richard> tor will launch from the cmdline no issue if i set the LD_LOAD_PATH appropriately first pointing to the shipped libs
<richard> if i first make build and make deploy
<richard> then copy the old/shipped firefox over the built firefox bin (but leave the rest as is) then everything launches fine
<richard> and finally
<richard> if i build a locally copy of tor, and drop it over the shipped version everything is fine
<richard> so if i build all the bins with the same toolchain (firefox and tor) then everything works fine
<richard> mix and match makes things sad
<richard> and a fresh un-touched 12.0a4 alpha also runs fine
<richard> anyway i'm unblocked for now and will open a ticket with the above findings and we can deal with it later
<ma1> is mix & match on any system something we actually (want to) support?
<richard> no, it's purely a build/development problem
<ma1> yes, I mean for developers.
<richard> yes we def want to support that :D
<richard> either that or we integrate tor into the tor-browser build process
<richard> :p
<richard> or some other smart solution
<ma1> I mean, doesn't mach boostrap install a local toolchain to work-around compat issues like this? Or am I completely missing the point?
<richard> so I *think* the problem is that my local dev firefox is being built with different versions of libs than the tor we ship with
<richard> and the deploy step we do is 'download the built bundle, copy our local firefox bins over'
<richard> so you get a mismatch of toolchaisn used for firefox vs tor 
<richard> but like i said more investigation is needed to see what is actually failing
<richard> my desktop's clang  is also now on version 14 vs my laptop on version 10 which who knows if that makes a difference vOv
<richard> (laptop dev env works fine, but i didn't do an OS upgrade there)

So the work-around is to build a local copy of tor, and deploy that over .binaries/dev/Browser/TorBrowser/Tor/tor. My best hypothesis so far is that tor is inheriting some sort of LD_FOO variable from firefox but we would need to look into this further.