Ben Gamari authored Sep 10, 2021 and Marge Bot committed Oct 12, 2021

Previously it was unclear whether req_shared_libs should require:

 * that the platform supports dynamic library loading,
 * that GHC supports dynamic linking of Haskell code, or
 * that the dyn way libraries were built

Clarify by splitting the predicate into two:

 * `req_dynamic_lib_support` demands that the platform support dynamic
   linking
 * `req_dynamic_hs` demands that the GHC support dynamic linking of
   Haskell code on the target platform

Naturally `req_dynamic_hs` cannot be true unless
`req_dynamic_lib_support` is also true.