Don't get host RTS ways via settings (#18651)

To correctly perform a linking hack for Windows we need to link with the
RTS GHC is currently using. We used to query the RTS ways via the
"settings" file but it is fragile (#18651). The hack hasn't been fixed
to take into account all the ways (Tracing) and it makes linking of GHC
with another RTS more difficult (we need to link with another RTS and to
regenerate the settings file).

So this patch uses the ways reported by the RTS itself
(GHC.Platform.Ways.hostWays) instead of the "settings" file.