Hadrian: don't accept the p_dyn way for executables

This tweaks the prof flavour to set "dynamic ghc programs" to false, and changes programContext so as to never again produce contexts for executables with the p_dyn way. With this patch, if we have ghcProfiled = True, then executables will always lean towards the profiling context, completely ignoring the "dynamic ghc programs" field, just like the make build system does: https://gitlab.haskell.org/ghc/ghc/blob/master/ghc/ghc.mk#L67. If ghcProfiled = False, then the dynamic way can take over.

This seems like a reasonable fix, at least until all our tooling is ready to deal with all sorts of composite ways.

This fixes builds with --flavour=prof, the problem is described in #16562 (closed).