Revert "Revert ad15c2, which causes Windows seg-faults (Trac #8834)"

This reverts commit a79613a75c7da0d3d225850382f0f578a07113b5.
windows: Fix #8870

This bumps the amount of default reserved and committed stack for GHC
executables to 8mb, to work around #8870. A proper fix should happen in
7.8.2

See note [Windows stack usage] in SysTools for the details.

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