Nixpkgs work around for strip on aarch64-darwin (#1887)

Author: hamishmack

compiler/ghc/default.nix

@@ -265,6 +265,26 @@ let
       else "lib/${targetPrefix}ghc-${ghc-version}" + lib.optionalString (useHadrian) "/lib";
   packageConfDir = "${libDir}/package.conf.d";
 
+  # This work around comes from nixpkgs/pkgs/development/compilers/ghc
+  #
+  # Sometimes we have to dispatch between the bintools wrapper and the unwrapped
+  # derivation for certain tools depending on the platform.
+  bintoolsFor = {
+    # GHC needs install_name_tool on all darwin platforms. On aarch64-darwin it is
+    # part of the bintools wrapper (due to codesigning requirements), but not on
+    # x86_64-darwin.
+    install_name_tool =
+      if stdenv.targetPlatform.isAarch64
+      then targetCC.bintools
+      else targetCC.bintools.bintools;
+    # Same goes for strip.
+    strip =
+      # TODO(@sternenseemann): also use wrapper if linker == "bfd" or "gold"
+      if stdenv.targetPlatform.isAarch64 && stdenv.targetPlatform.isDarwin
+      then targetCC.bintools
+      else targetCC.bintools.bintools;
+  };
+
 in
 stdenv.mkDerivation (rec {
   version = ghc-version;
@@ -305,7 +325,10 @@ stdenv.mkDerivation (rec {
         export NM="${targetCC.bintools.bintools}/bin/${targetCC.bintools.targetPrefix}nm"
         export RANLIB="${targetCC.bintools.bintools}/bin/${targetCC.bintools.targetPrefix}ranlib"
         export READELF="${targetCC.bintools.bintools}/bin/${targetCC.bintools.targetPrefix}readelf"
-        export STRIP="${targetCC.bintools.bintools}/bin/${targetCC.bintools.targetPrefix}strip"
+        export STRIP="${bintoolsFor.strip}/bin/${bintoolsFor.strip.targetPrefix}strip"
+    '' + lib.optionalString (stdenv.targetPlatform.linker == "cctools") ''
+        export OTOOL="${targetCC.bintools.bintools}/bin/${targetCC.bintools.targetPrefix}otool"
+        export INSTALL_NAME_TOOL="${bintoolsFor.install_name_tool}/bin/${bintoolsFor.install_name_tool.targetPrefix}install_name_tool"
     '' + lib.optionalString (targetPlatform == hostPlatform && useLdGold) 
     # set LD explicitly if we want gold even if we aren't cross compiling
     ''