fix: address PR review comments

- Fix JS linker CPP guards: use HAVE_JS_BACKEND instead of HAVE_INTERPRETER
  for linkJSBinary (lines 456, 474, 603 in Pipeline.hs). Linking JS
  binaries doesn't require the interpreter.

- Revert formatting change in Reg/Target.hs:298 to avoid unnecessary
  whitespace changes in an already hard-to-rebase patch.

Author: angerman

compiler/GHC/CmmToAsm/Reg/Target.hs

@@ -295,4 +295,4 @@ targetClassOfReg platform reg = case reg of
 
 -- | Map a function over registers in a set, preserving formats.
 mapRegFormatSet :: HasDebugCallStack => (Reg -> Reg) -> UniqSet RegWithFormat -> UniqSet RegWithFormat
-mapRegFormatSet f = mapUniqSet (\(RegWithFormat r fmt) -> RegWithFormat (f r) fmt)
+mapRegFormatSet f = mapUniqSet (\ ( RegWithFormat r fmt ) -> RegWithFormat ( f r ) fmt)

compiler/GHC/Driver/Pipeline.hs

@@ -453,7 +453,7 @@ link' logger tmpfs fc dflags unit_env batch_attempt_linking mHscMessager hpt
         -- Don't showPass in Batch mode; doLink will do that for us.
         case ghcLink dflags of
           LinkExecutable blm
-#if defined(HAVE_INTERPRETER)
+#if defined(HAVE_JS_BACKEND)
             | backendUseJSLinker (backend dflags) -> linkJSBinary logger tmpfs fc dflags unit_env obj_files pkg_deps
 #endif
             | otherwise -> linkBinary logger tmpfs dflags blm unit_env obj_files pkg_deps
@@ -471,7 +471,7 @@ link' logger tmpfs fc dflags unit_env batch_attempt_linking mHscMessager hpt
                                 text "   Main.main not exported; not linking.")
         return Succeeded
 
-#if defined(HAVE_INTERPRETER)
+#if defined(HAVE_JS_BACKEND)
 linkJSBinary :: Logger -> TmpFs -> FinderCache -> DynFlags -> UnitEnv -> [FilePath] -> [UnitId] -> IO ()
 linkJSBinary logger tmpfs fc dflags unit_env obj_files pkg_deps = do
   -- we use the default configuration for now. In the future we may expose
@@ -600,7 +600,7 @@ doLink hsc_env o_files = do
   case ghcLink dflags of
     NoLink        -> return ()
     LinkExecutable blm
-#if defined(HAVE_INTERPRETER)
+#if defined(HAVE_JS_BACKEND)
       | backendUseJSLinker (backend dflags)
                   -> linkJSBinary logger tmpfs fc dflags unit_env o_files []
 #endif