v8: fix darwin build

pkgs/development/libraries/v8/default.nix

···
 , gn, ninja, python3, glib, pkg-config, icu
 , xcbuild, darwin
 , fetchpatch
+, llvmPackages
+, symlinkJoin
 }:
 
 # Use update.sh to update all checksums.
···
     touch build/config/gclient_args.gni
   '';
 
+  llvmCcAndBintools = symlinkJoin { name = "llvmCcAndBintools"; paths = [ stdenv.cc llvmPackages.llvm ]; };
+
   gnFlags = [
     "use_custom_libcxx=false"
     "is_clang=${lib.boolToString stdenv.cc.isClang}"
···
     # ''custom_toolchain="//build/toolchain/linux/unbundle:default"''
     ''host_toolchain="//build/toolchain/linux/unbundle:default"''
     ''v8_snapshot_toolchain="//build/toolchain/linux/unbundle:default"''
-  ] ++ lib.optional stdenv.cc.isClang ''clang_base_path="${stdenv.cc}"'';
+  ] ++ lib.optional stdenv.cc.isClang ''clang_base_path="${llvmCcAndBintools}"''
+  ++ lib.optional stdenv.isDarwin ''use_lld=false'';
 
   NIX_CFLAGS_COMPILE = "-O2";
   FORCE_MAC_SDK_MIN = stdenv.targetPlatform.sdkVer or "10.12";
···
     python3
   ] ++ lib.optionals stdenv.isDarwin [
     xcbuild
-    darwin.DarwinTools
+    llvmPackages.llvm
     python3.pkgs.setuptools
   ];
   buildInputs = [ glib icu ];
···
     maintainers = with maintainers; [ cstrahan proglodyte matthewbauer ];
     platforms = platforms.unix;
     license = licenses.bsd3;
-    # Fails to build on Darwin, see https://github.com/NixOS/nixpkgs/issues/158076
-    broken = stdenv.isDarwin;
   };
 }

pkgs/development/ruby-modules/gem-config/default.nix

···
     buildInputs = [ which v8 python2 ];
     buildFlags = [ "--with-system-v8=true" ];
     dontBuild = false;
+    # The gem includes broken symlinks which are ignored during unpacking, but
+    # then fail during build. Since the content is missing anyway, touching the
+    # files is enough to unblock the build.
+    preBuild = ''
+      touch vendor/depot_tools/cbuildbot vendor/depot_tools/chrome_set_ver vendor/depot_tools/cros_sdk
+    '';
     postPatch = ''
       substituteInPlace ext/libv8/extconf.rb \
         --replace "location = Libv8::Location::Vendor.new" \

pkgs/top-level/all-packages.nix

···
     inherit (darwin) libobjc;
   };
   defaultGemConfig = callPackage ../development/ruby-modules/gem-config {
-    # recent v8 doesn't build on nixpkgs Darwin yet. https://github.com/NixOS/nixpkgs/issues/158076
-    v8 = if stdenv.isDarwin then v8_8_x else v8;
     inherit (darwin) DarwinTools cctools;
     inherit (darwin.apple_sdk.frameworks) CoreServices;
   };
···
 
   ucommon = callPackage ../development/libraries/ucommon { };
 
-  v8 = callPackage ../development/libraries/v8 { };
+  v8 = darwin.apple_sdk_11_0.callPackage ../development/libraries/v8 { };
 
   v8_8_x = callPackage ../development/libraries/v8/8_x.nix { };