qtwebengine: switch to pure sandbox on darwin

pkgs/development/libraries/qt-5/modules/qtwebengine.nix

···
     '' else ''
     substituteInPlace src/3rdparty/chromium/base/mac/mach_port_broker.mm \
       --replace "audit_token_to_pid(msg.trailer.msgh_audit)" "msg.trailer.msgh_audit.val[5]"
-    '')
-    + ''
-    substituteInPlace src/3rdparty/chromium/sandbox/mac/BUILD.gn \
-      --replace 'libs = [ "sandbox" ]' 'libs = [ "/usr/lib/libsandbox.1.dylib" ]'
-    '');
+    ''));
 
   NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isGNU [
     # with gcc8, -Wclass-memaccess became part of -Wall and this exceeds the logging limit
···
 
   buildInputs = optionals stdenv.isDarwin (with darwin; [
     cups
+    apple_sdk.libs.sandbox
 
     # `sw_vers` is used by `src/3rdparty/chromium/build/config/mac/sdk_info.py`
     # to get some information about the host platform.
···
         shift
       done
     '')
-
-    # For sandbox.h include
-    (runCommand "MacOS_SDK_sandbox.h" {} ''
-      install -Dm444 "${lib.getDev darwin.apple_sdk.sdk}"/include/sandbox.h "$out"/include/sandbox.h
-    '')
   ]);
-
-  __impureHostDeps = optional stdenv.isDarwin "/usr/lib/libsandbox.1.dylib";
 
   dontUseNinjaBuild = true;
   dontUseNinjaInstall = true;