compile with clang-12 errors

Trying to compile octave with clang-12. It wants size_t to be std:size_t:

<<<<
libtool: compile:  clang++ -DHAVE_CONFIG_H -I. -I.. -DOCTAVE_DLL
-DEXTERNAL_DLL -Iliboctave -I../liboctave -I../liboctave/array
-Iliboctave/numeric -I../liboctave/numeric -Iliboctave/operators
-I../liboctave/operators -I../liboctave/system -I../liboctave/util
-I../liboctave/wrappers -fPIC -pthread -fopenmp -Wall -W -Wshadow
-Woverloaded-virtual -Wold-style-cast -Wformat -Wpointer-arith
-Wwrite-strings -Wcast-align -Wcast-qual -fvisibility=hidden -g -O2 -MT
liboctave/util/libutil_la-action-container.lo -MD -MP -MF
liboctave/util/.deps/libutil_la-action-container.Tpo -c
../liboctave/util/action-container.cc  -fPIC -DPIC -o
liboctave/util/.libs/libutil_la-action-container.o
In file included from ../liboctave/util/action-container.cc:30:
../liboctave/util/action-container.h:199:26: error: unknown type name
'size_t'; did you mean 'std::size_t'?
    OCTAVE_API void run (size_t num);
                         ^~~~~~
                         std::size_t
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/x86_64-redhat-linux/bits/c++config.h:2427:26:
note: 'std::size_t' declared here
  typedef __SIZE_TYPE__         size_t;
                                ^
In file included from ../liboctave/util/action-container.cc:30:
../liboctave/util/action-container.h:205:19: error: unknown type name
'size_t'; did you mean 'std::size_t'?
    void discard (size_t num)
                  ^~~~~~
                  std::size_t
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/x86_64-redhat-linux/bits/c++config.h:2427:26:
note: 'std::size_t' declared here
  typedef __SIZE_TYPE__         size_t;
                                ^
In file included from ../liboctave/util/action-container.cc:30:
../liboctave/util/action-container.h:216:13: error: unknown type name
'size_t'; did you mean 'std::size_t'?
    virtual size_t size (void) const = 0;
            ^~~~~~
            std::size_t
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/x86_64-redhat-linux/bits/c++config.h:2427:26:
note: 'std::size_t' declared here
  typedef __SIZE_TYPE__         size_t;
                                ^
In file included from ../liboctave/util/action-container.cc:30:
../liboctave/util/action-container.h:210:12: error: unknown type name
'size_t'; did you mean 'std::size_t'?
      for (size_t i = 0; i < num; i++)
           ^~~~~~
           std::size_t
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/x86_64-redhat-linux/bits/c++config.h:2427:26:
note: 'std::size_t' declared here
  typedef __SIZE_TYPE__         size_t;
                                ^
4 errors generated.

>>>>