[C++] Can't build Arrow with Substrait on Ubuntu 20.04

[100%] Building CXX object src/arrow/engine/CMakeFiles/arrow_substrait_objlib.dir/substrait/type_internal.cc.o
/home/dewey/Desktop/r/arrow/cpp/src/arrow/engine/substrait/expression_internal.cc: In function ‘arrow::Status arrow::engine::DecodeArg(const substrait::FunctionArgument&, int, arrow::engine::SubstraitCall*, const arrow::engine::ExtensionSet&, const arrow::engine::ConversionOptions&)’:
/home/dewey/Desktop/r/arrow/cpp/src/arrow/engine/substrait/expression_internal.cc:60:21: error: ‘bool substrait::FunctionArgument::has_enum_() const’ is private within this context
   60 |   if (arg.has_enum_()) {
      |                     ^
In file included from /home/dewey/Desktop/r/arrow/cpp/src/arrow/engine/substrait/expression_internal.h:30,
                 from /home/dewey/Desktop/r/arrow/cpp/src/arrow/engine/substrait/expression_internal.cc:20:
/home/dewey/.r-arrow-dev-build/build/substrait_ep-generated/substrait/algebra.pb.h:21690:13: note: declared private here
21690 | inline bool FunctionArgument::has_enum_() const {
      |             ^~~~~~~~~~~~~~~~
[100%] Building CXX object src/arrow/engine/CMakeFiles/arrow_substrait_objlib.dir/substrait/util.cc.o
make[2]: *** [src/arrow/engine/CMakeFiles/arrow_substrait_objlib.dir/build.make:76: src/arrow/engine/CMakeFiles/arrow_substrait_objlib.dir/substrait/expression_internal.cc.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:2028: src/arrow/engine/CMakeFiles/arrow_substrait_objlib.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

$ protoc --version
libprotoc 3.6.1