haskell.compiler.{ghc98*,ghcHEAD}: bootstrap using source built 9.6

Unfortunately, we are running into trouble linking dependencies of
hadrian against the libraries of the clock package with 9.6.3 and
9.6.4 _bindists_. My current suspiscion is that this is caused by
some kind of discrepancy between the toolchain used by GHC upstream
and us that persists from the configure step used when building the
bindist. The problem seems to be somewhat localized to hsc2hs (hence
clock is an issue), with GHC 9.6.4 bindists even passing a flag to
ld that is not supported by our version of cctools.

The problem is not fully diagnosed, so take the speculation above
with a grain of salt.

As a workaround, we can use the source built GHC 9.6 which is, of
course, configured with our toolchain in the environment.

pkgs/development/compilers/ghc/9.6.3-binary.nix

···
     # `pkgsMusl`.
     platforms = builtins.attrNames ghcBinDists.${distSetName};
     maintainers = lib.teams.haskell.members;
+    # packages involving hsc2hs (clock) produce libraries our
+    # ld can't link against
+    broken = stdenv.hostPlatform.isDarwin;
   };
 }

pkgs/top-level/haskell-packages.nix

···
           packages.ghc963
         else if stdenv.hostPlatform.isPower64 && stdenv.hostPlatform.isLittleEndian then
           packages.ghc963
+        else if stdenv.hostPlatform.isDarwin then
+          # it seems like the GHC 9.6.* bindists are built with a different
+          # toolchain than we are using (which I'm guessing from the fact
+          # that 9.6.4 bindists pass linker flags our ld doesn't support).
+          # With both 9.6.3 and 9.6.4 binary it is impossible to link against
+          # the clock package (probably a hsc2hs problem).
+          packages.ghc963
         else
           packages.ghc963Binary;
       inherit (buildPackages.python3Packages) sphinx;
···
           packages.ghc963
         else if stdenv.hostPlatform.isPower64 && stdenv.hostPlatform.isLittleEndian then
           packages.ghc963
+        else if stdenv.hostPlatform.isDarwin then
+          # it seems like the GHC 9.6.* bindists are built with a different
+          # toolchain than we are using (which I'm guessing from the fact
+          # that 9.6.4 bindists pass linker flags our ld doesn't support).
+          # With both 9.6.3 and 9.6.4 binary it is impossible to link against
+          # the clock package (probably a hsc2hs problem).
+          packages.ghc963
         else
           packages.ghc963Binary;
       inherit (buildPackages.python3Packages) sphinx;
···
         if stdenv.hostPlatform.isAarch32 then
           packages.ghc963
         else if stdenv.hostPlatform.isPower64 && stdenv.hostPlatform.isLittleEndian then
+          packages.ghc963
+        else if stdenv.hostPlatform.isDarwin then
+          # it seems like the GHC 9.6.* bindists are built with a different
+          # toolchain than we are using (which I'm guessing from the fact
+          # that 9.6.4 bindists pass linker flags our ld doesn't support).
+          # With both 9.6.3 and 9.6.4 binary it is impossible to link against
+          # the clock package (probably a hsc2hs problem).
           packages.ghc963
         else
           packages.ghc963Binary;