GHC built on macOS Mojave nondeterministically segfaults
I am seeing perhaps a quarter of GHC builds on the GitLab Darwin builder (running Mojave) fail with a segfault in
ghc-stage1. Unfortunately I've been entirely unable to reproduce this in a debugger (which isn't surprising given the low probability of the crash manifesting).
Given that we haven't seen this in any Darwin builds until now I'm suspicious of either the XCode toolchain or Mojave itself.