v8: unpin llvmPackages_15.stdenv on darwin

pkgs/development/libraries/v8/default.nix

···
         --replace 'current_toolchain == host_toolchain || !use_xcode_clang' \
                   'false'
     ''}
-    ${lib.optionalString (stdenv.isDarwin && stdenv.isx86_64) ''
+    ${lib.optionalString stdenv.isDarwin ''
       substituteInPlace build/config/compiler/BUILD.gn \
         --replace "-Wl,-fatal_warnings" ""
     ''}
···
   ] ++ lib.optional stdenv.cc.isClang ''clang_base_path="${llvmCcAndBintools}"''
   ++ lib.optional stdenv.isDarwin ''use_lld=false'';
 
-  env.NIX_CFLAGS_COMPILE = "-O2";
+  env.NIX_CFLAGS_COMPILE = toString ([
+    "-O2"
+  ] ++ lib.optionals stdenv.cc.isClang [
+    "-Wno-error=enum-constexpr-conversion"
+  ]);
   FORCE_MAC_SDK_MIN = stdenv.hostPlatform.sdkVer or "10.12";
 
   nativeBuildInputs = [

pkgs/top-level/all-packages.nix

···
 
   ucommon = callPackage ../development/libraries/ucommon { };
 
-  v8 = callPackage ../development/libraries/v8 (
-    let
-      stdenv' = if stdenv.cc.isClang && lib.versionAtLeast (lib.getVersion stdenv.cc.cc) "16"
-        then overrideLibcxx llvmPackages_15.stdenv
-        else stdenv;
-    in
-    {
-      stdenv = if stdenv'.isDarwin then overrideSDK stdenv' "11.0" else stdenv';
-    }
-  );
+  v8 = callPackage ../development/libraries/v8 {
+    stdenv = if stdenv.isDarwin then overrideSDK stdenv "11.0" else stdenv;
+  };
 
   intel-vaapi-driver = callPackage ../development/libraries/intel-vaapi-driver { };