Sylvain Henry authored Jun 22, 2021 and Marge Bot committed Jul 01, 2021

Use DiagOpts for diagnostic options instead of directly querying
DynFlags (#17957).

Surprising performance improvements on CI:

  T4801(normal) ghc/alloc   313236344.0   306515216.0  -2.1% GOOD
  T9961(normal) ghc/alloc   384502736.0   380584384.0  -1.0% GOOD
  ManyAlternatives(normal) ghc/alloc   797356128.0   786644928.0  -1.3%
  ManyConstructors(normal) ghc/alloc  4389732432.0  4317740880.0  -1.6%
  T783(normal) ghc/alloc   408142680.0   402812176.0  -1.3%

Metric Decrease:
    T4801
    T9961
    T783
    ManyAlternatives
    ManyConstructors

Bump haddock submodule