Fully drop `settings` in favor of per-target configuration
Following #24212, where GHC now uses the structure `GHC.Toolchain.Target.Target` representation, we should make sure that there are no longer any global `settings` file.
Instead, all target configuration options should be configured per-target to a `Target` file. See https://gitlab.haskell.org/ghc/ghc/-/issues/24212#note_627120
- [x] ("unlit command", "$topdir/../bin/unlit")
- [x] ("target has libm", "YES")
- [x] ("target RTS linker only supports shared libraries", "NO")
- [x] ("Use interpreter", "YES")
- [x] ("Support SMP", "YES")
- [ ] ("RTS ways", "v thr thr_debug thr_debug_dyn thr_dyn debug debug_dyn dyn")
- [x] ("RTS expects libdw", "NO")
- [ ] ("Relative Global Package DB", "package.conf.d")
- [ ] ("base unit-id", "base-4.21.0.0-inplace")
MR: !14554
issue