julia

107901d0 - Try to avoid julia becoming unkillable after fatal errors (#40056)

Try to avoid julia becoming unkillable after fatal errors (#40056) - don't smash the alt-stack when already using it - handle jl_critical_error on the original stack, leaving our signal handling thread free to handle more signals (and helping lock corruption detection in some cases) - unblock signals when handling signals: some libc apparently like to block all signals, which can cause mild havoc, since we'd really like the user or bad data to be able to still kill the process (and not just be ignored or cause it to hang) - reset signals to SIG_DFL earlier (so we recurse less) - destroy some state from the Task we co-opted to run the exit handlers, so that it can't accidentally jump back into the running program after we've started tearing down the process, from an untimely ^C (previously ^C might cancel the exit) or a jlbacktrace call. - mark functions as leaf with CFI instead of (potentially) smashing the stack, and add a bit of red-zone if we are recursing (to keep pgcstack sensible) - support safe_restore for the mach catch_exception_raise (while we're trying to generate the backtrace)