driver: always merge objects when possible

This patch makes the driver always merge objects with `ld -r` when
possible, and only fall back to calling `ar -L` when merge objects
command is unavailable. This completely reverts !8887 and !12313,
given more fixes in Cabal seems to be needed to avoid breaking certain
configurations and the maintainence cost is exceeding the behefits in
this case :/

compiler/GHC/Driver/Pipeline/Execute.hs

@@ -1045,17 +1045,12 @@ However, `ld -r` is broken in some cases:
  * The LLD linker that we use on Windows does not support the `-r`
    flag needed to support object merging (see #21068). For this reason
    on Windows we do not support GHCi objects.
- * `wasm-ld -r` is prohibitively slow, especially when handling large
-   input objects (e.g. profiled objects).
 
 In these cases, we bundle a module's own object file with its foreign
 stub's object file, instead of merging them. Consequently, we can end
 up producing `.o` files which are in fact static archives. This can
 only work if `ar -L` is supported, so the archive `.o` files can be
-properly added to the final static library. We must also take care not
-to produce archive `.dyn_o` when building dynamic objects, otherwise
-we end up with broken `.so` files when GHC is built with `llvm-ar`
-(#22210).
+properly added to the final static library.
 
 Note that this has somewhat non-obvious consequences when producing
 initializers and finalizers. See Note [Initializers and finalizers in Cmm]
@@ -1081,7 +1076,7 @@ via gcc.
 -- | See Note [Object merging].
 joinObjectFiles :: HscEnv -> [FilePath] -> FilePath -> IO ()
 joinObjectFiles hsc_env o_files output_fn
-  | can_merge_objs && (not dashLSupported || is_dyn) = do
+  | can_merge_objs = do
   let toolSettings' = toolSettings dflags
       ldIsGnuLd = toolSettings_ldIsGnuLd toolSettings'
       ld_r args = GHC.SysTools.runMergeObjects (hsc_logger hsc_env) (hsc_tmpfs hsc_env) (hsc_dflags hsc_env) (
@@ -1109,7 +1104,6 @@ joinObjectFiles hsc_env o_files output_fn
   withAtomicRename output_fn $ \tmp_ar ->
       liftIO $ runAr logger dflags Nothing $ map Option $ ["qc" ++ dashL, tmp_ar] ++ o_files
   where
-    is_dyn = ways dflags `hasWay` WayDyn
     dashLSupported = sArSupportsDashL (settings dflags)
     dashL = if dashLSupported then "L" else ""
     can_merge_objs = isJust (pgm_lm (hsc_dflags hsc_env))