Hi,

Last year I've provided a patch that enables DTrace probes under FreeBSD, sadly as it turns
out this currently breaks the ability of GHC 8.4.1 to function as a bootstrap compiler under
FreeBSD. I've provided a patch that adds a flag to the build system so one can turn off DTrace
in case one needs to build a bootstrap compiler.

https://phabricator.haskell.org/D4575

This should probably also contain some heads up in the documentation, otherwise someone might
end up with a compiler that's not suitable for bootstrapping. Not sure on how this is being handled.

I have an idea on how to fix the actual issue but for the time being this might be a suitable workaround.
Maybe we can still get this into 8.4.2? I've already notified the FreeBSD ports maintainers regarding this
issue.

Sorry for the inconvenience.

Kind regards,
raichoo