Unfortunately, we can't completely remove or skip include/execvpe.h
and cbits/execvpe.c, because they also contain pPrPr_disableITimers(),
which is called from the Haskell code.
- Switch back to GhcThreaded=YES (default). It's stupid, it's not
required by GHC (IIRC it was required a long time ago back when
ghci used libreadline), but it may help finding rthread bugs.
Until now, I did run four complete builds of GHC and all Haskell
ports with dpb without any problems.
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