Fix #8754 in a round-about way.

For some reason on OS X, it seems like -Bsymbolic (which we use for
hooks into the RTS) isn't working, which results in #8754, where stats
don't work because defaultHooks doesn't initialize the stats flag. This
seems to work on Linux static/dynamically, but only on OS X statically.

After talking with Simon, really, the entire hooks thing is a bit
fragile. For now, we just work around it (since GHCi is dynamically
linked) by calling into the defaultHooks ourselves when GHC starts.

Signed-off-by: Austin Seipp <austin@well-typed.com>

(cherry picked from commit 5023c91780e90947680fe0640f7564a4f6448bea)
Add comments explaining #8754

Signed-off-by: Austin Seipp <austin@well-typed.com>

(cherry picked from commit b626c3d4ce0e66216705ba8355c914dc809e3fe7)