decoder says we don't need them and the build time on these builds is already 4+ hours.
Would it be sufficient if I just disable jit-tests for asan debug builds? I measured make check without jit-tests and it only takes 10 minutes on my machine, while jit-tests take almost an hour. That would also ensure that the debug build gets at least some testing to ensure it's not entirely broken. That would also be an easy change in js/src/Makefile.in. If you want to disable it entirely, then the better way might be to do it in buildbot.
Right now, the two are attached at the hip, so either both run or neither run. However, part of why I raised this issue with you in the first place was due to the upcoming splitting of Cpp and Jit out of the build process and into their own jobs. I wanted to make sure we were on the same page about what we're running now and what we want running then.
Debug ASAN builds take about 90min tops these days, even with some checktests still running. I don't think this is worth doing anything about at this point.